Physics previous year question Of Optics for NDA

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previous year question Of Optics for NDA

previous year question

Q 2868867705

Consider the following statement(s)

I. The focal length of the objective of a microscope is
less than the focal length of the eyepiece.

II. The minimum distance between an object and its real image
formed by a convex lens of focal length r is equal to 4(.

Which of the statement(s) given above is/are correct?

(A)

Only I

(B)

Only II

(C)

Both I and II

(D)

Neither I nor II

Solution:

Correct Answer is `=>` (A) Only I

Q 2848867703

Match List I (Defect in vision) with List II (Correcting lens) and
select the correct answer using the codes gives below the lists

Column I		Column II
(A)	Short sight or myopia	(1)	Cylindrical lens
(B)	Long sight or hypermetropia	(2 )	Bifocal lens
(C)	Presbyopia	(3)	Convex lens
(D)	Astigmatism	(4)	Concave lens

Codes

A B C D A B C D

(A)

4321

(B)

3421

(C)

4231

(D)

3214

Solution:

Correct Answer is `=>` (C) 4231

Q 2878767606

Consider the following statement(s)

I. Compound microscope has an objective lens with a very
short focal length.

II. Simple microscope is of a strong converging lens system.

III. Television camera converts the optical image into
electrical video signals.

IV. Hypermetropia is corrected by using a diverging lens.

Which of the statement(s) given
above is/are correct?

(A)

Only IV

(B)

I, II and Ill

(C)

All of these

(D)

Both II and Ill

Solution:

Correct Answer is `=>` (B) I, II and Ill

Q 2828667501

Which of the following pairs are correctly matched ?

I. Power of lens : diopter

II. Two waves of E a me frequency: diffraction and amplitude
having constant phase difference optical fibre

III. Total internal reflection optical fibre

IV. Change of focal length of alens with colour : spherical
aberration

(A)

Both Il and IV

(B)

I, II and Ill

(C)

II, Ill and IV

(D)

Both I and Ill

Solution:

Correct Answer is `=>` (D) Both I and Ill

Q 2808567408

Which of the following are true regarding image formation with
the help of mirrors?

I. A concave mirror can give a diminished virtual image.

II. A concave mirror can give a real image.

III. A convex mirror can give a virtual image.

IV. A convex mirror cannot give a real image.

Select the correct answer from the codes given below

(A)

Both I and Ill

(B)

Both I and IV

(C)

I, Ill and IV

(D)

II, Ill and IV

Solution:

Correct Answer is `=>` (D) II, Ill and IV

Q 2888567407

(A)

Both I and Ill

(B)

Both I and IV

(C)

I, Ill and IV

(D)

II, Ill and IV

Solution:

Correct Answer is `=>` (D) II, Ill and IV

Q 2868567405

Consider the following statements

I. In a periscope, prisms are used to turn the incoming light
through `90^o` .

II. In a periscope, plane mirrors can also the used instead of
prisms.

III. The loss of intensity of light is more in the case of reflections
by a mirror.

Which of the statements given above are correct?

(A)

Both II and Ill

(B)

Both I and II

(C)

All of these

(D)

Both I and Ill

Solution:

Correct Answer is `=>` (B) Both I and II

Q 2818567400

Which one of the following can be used to focus sun light?

(A)

Plane mirror

(B)

Concave lens

(C)

Concave mirror

(D)

Convex mirror

Solution:

Correct Answer is `=>` (C) Concave mirror

Q 2878467306

Two convex lenses of focal lengths `f_1`, and `f_2` are separated by a
distance d. The combination will work as a glass slab, if

(A)

`d= f_1 + f_2`

(B)

`d < f_1 + f_2`

(C)

`d > f_1 + f_2`

(D)

`d ge f_1 + f_2`

Solution:

Correct Answer is `=>` (A) `d= f_1 + f_2`

Q 2848467303

Suppose that a light wave propagates from a point A to
another point Band we introduce into its path a glass plate
`( μ_8 = 1.33)` of thickness `t = 1 mm`. If `λ_0 = 500 nm ` is; at A, then the
change in wavelength of the wave at B is

(A)

1000 wavelength

(B)

1500 wavelength

(C)

2500 wavelength

(D)

3000 wavelength

Solution:

Correct Answer is `=>` (A) 1000 wavelength

Q 2818367209

In a motor car, spherical mirrors are utilised at two different places,

(i) the head light and
(ii) rear view mirror.

What type of mirrors are used?

(A)

concave for case (i) and convex for case (ii)

(B)

convex for case (i) and concave for case (ii)

(C)

concave for both cases

(D)

convex for both cases

Solution:

Correct Answer is `=>` (A) concave for case (i) and convex for case (ii)

Q 2868367205

A plane mirror lies face up, making an angle of `15^o` with the horizontal.
A ray of light coming down vertically on the mirror. The angle
of incidence, the angle between the reflected ray and the horizontal are
respectively

(A)

`10^o , 20^o`

(B)

`15^o, 15^o`

(C)

`15^o , 30^o`

(D)

`15^o , 60^o`

Solution:

Correct Answer is `=>` (D) `15^o , 60^o`

Q 2848367203

Two plane mirrors are inclined at an angle of `60^o` to each other. If an
object is placed between them, then the number of images
produced will be

(A)

(B)

(C)

(D)

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (A) 5

Q 2818367200

Which one of the following is used to remove astigmatism for a
human eye?

(A)

Concave lens

(B)

Convex lens

(C)

Convex lens

(D)

Prismatic lens

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (C) Convex lens

Q 2808267108

Defect of colour blindness can be remedied by the use of

(A)

cylindrical lens

(B)

bifocal lens

(C)

contact lens

(D)

None of these

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (D) None of these

Q 2888267107

The region of retina in which the vision is most acute is

(A)

conjunctiva

(B)

ciliary body

(C)

fovea centralis

(D)

vitreous humour

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (C) fovea centralis

Q 2868267105

The human eye has essentially a lens and a retina used as a screen.
Which one of the following statements is true about this
combination of lens and retina?

(A)

It is a convex lens with variable focal length and at a fixed distance between the retina and the lens

(B)

It is a convex lens with variable focal length and its distance from the retina

(C)

It is a convex lens of constant focal length at a fixed distance from the retina

(D)

It is a concave lens of adjustable focal length at a fixed distance from the retina

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (A) It is a convex lens with variable focal length and at a fixed distance between the retina and the lens

Q 2848267103

In a healthy human eye, the focussing is done by

(A)

the change in the convexity of the lens through ciliary muscles

(B)

changing in the refractive index of the eye fluid

(C)

changing curvature of retina

(D)

to and from movement of the eye lens

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (A) the change in the convexity of the lens through ciliary muscles

Q 2838267102

Which one of the following is correct? Large aperture telescopes
are used for

(A)

greater resolution

(B)

greater magnification

(C)

reducing lens aberration

(D)

ease of manufacture

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (A) greater resolution

Q 2828267101

Focal length of the eye lens which enables us to see the object at
varying distances, is controlled and changed by

(A)

retina

(B)

ciliary muscles

(C)

choroid

(D)

vitreous humour

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (B) ciliary muscles

Q 2818167009

Which one of the following optical instruments produce a virtual
image?

(A)

A simple magnifier

(B)

Movie projector

(C)

An ordinary single lens reflex camera

(D)

None of the above

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (A) A simple magnifier

Q 2878167006

In Rayleigh scattering, the degree of Scattering is proportional to
fourth power of wavelength but the size of the scattering particles
of the medium should be

(A)

less than the wavelength used

(B)

equal to the wavelength used

(C)

atleast four times the wavelength used

(D)

three times the wavelength used

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (B) equal to the wavelength used

Q 2848167003

The magnifying power of a telescope can be increased by

(A)

increasing the diameter of the objective

(B)

reducing the focal length of eyepiece

(C)

reducing focal length of the objective

(D)

increase tho diameter of eyepiece

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (A) increasing the diameter of the objective

Q 2828167001

An air bubble inside water behaves as a

(A)

concave lens

(B)

concave convex lens

(C)

plano-convex lens

(D)

convex lens

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (A) concave lens

Q 2818156900

A convex lens is immersed in a liquid denser than glass. It will
be:nave as a

(A)

diverging lens

(B)

plane glass

(C)

convergent lens

(D)

optical axis

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (A) diverging lens

Q 2878056806

For a thin lens, the nodal points
coincide with

(A)

nodal planes

(B)

principal focii

(C)

optical centre

(D)

optional axis

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (C) optical centre

Q 2838056802

The inability of rays of different colours to converge at a single
point after refraction through a convex lens is called

(A)

coma

(B)

spherical aberration

(C)

chromatic aberration

(D)

distortion

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (C) chromatic aberration

Q 2818856700

A stereoscopic camera produces
an image, which is

(A)

magnified

(B)

three-dimensional

(C)

three-dimensional in appearance

(D)

coloured

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (C) three-dimensional in appearance

Q 2868756605

The order of colour in a secondary rainbow is

(A)

no regular pattern is observed

(B)

red on the inner edge and violet on the outer edge

(C)

red on the outer edge and violet on the inner edge

(D)

None of the above

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (B) red on the inner edge and violet on the outer edge

Q 2848756603

The wavelength of the light of violet colour is

(A)

4 micron

(B)

0.4 micron

(C)

0.04 micron

(D)

0.004 micron

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (B) 0.4 micron

Q 2818756600

Which one of the following colours has longest wavelength?

(A)

Green

(B)

Yellow

(C)

Blue

(D)

Red

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (D) Red

Q 2838656502

The stars twinkle at night because

(A)

they emit energy

(B)

of diffraction

(C)

of refraction

(D)

of reflection

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (C) of refraction

Q 2828656501

Rays of light get refracted while passing from air to glass because

(A)

density of glass is higher than that of air

(B)

they cannot be reflected from a glass surface

(C)

glass absorbs energy from the light rays

(D)

speed of light in glass is less than the !;peed of light in air

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (A) density of glass is higher than that of air

Q 2808556408

An astronaut in an the earth satellite will observe sky as

(A)

blue

(B)

red

(C)

white

(D)

black

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (A) blue

Q 2878556406

A beam of monochromatic is passing from one medium to
another. Which one of the following quantities does not change?

(A)

Amplitude

(B)

Velocity

(C)

Wavelength

(D)

Frequency

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (D) Frequency

Q 2838556402

If half of the body of a lens is converted with black paper, then
the image produced by the lens will

(A)

have its size reduced to half

(B)

disappear

(C)

have its intensity reduced to half

(D)

None of the above

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (C) have its intensity reduced to half

Q 2818556400

When a ray of light is reflected under multiple reflections by a
set of plane parallel mirrors, then the intensity of the ray
diminishes due to

(A)

absorption as well as scattering of light from the mirrors

(B)

scatering of light by the atmosphere

(C)

absorption of light by the atmosphere

(D)

None of the above

Solution:

Given, `theta = 60^o`

`:. n = (360^o )/(theta ) = 360/60 = 6 =` even

`=> ` Number of images `= 6-1 = 5`

Correct Answer is `=>` (A) absorption as well as scattering of light from the mirrors

Q 2808456308

If the refractive indices of water and that of glass with respect to
air are 4/3 and 3/2 respectively, then the refractive index of glass
with respect to water is

(A)

2.66

(B)

(C)

1.125

(D)

0.88

Solution:

Given, ` text()_(a)μ_g = 3/2 , text()_(a)μ_w = 4/3`,

` text()_(w)μ_g = ?`

We know that,

` text()_(w)μ_g = ( text()_(a)μ_g )/( text()_(a)μ_g) = (3/2)/( 4/3) = 9/8 = 1.125`

Correct Answer is `=>` (C) 1.125

Q 2868456305

The co erect sequence of the decreasing order of velocity of
light in glass, diamond and water is

(A)

diamond, glass, water

(B)

glass, diamond, water

(C)

diamond, water, glass

(D)

water, glass, diamond

Solution:

Given, ` text()_(a)μ_g = 3/2 , text()_(a)μ_w = 4/3`,

` text()_(w)μ_g = ?`

We know that,

` text()_(w)μ_g = ( text()_(a)μ_g )/( text()_(a)μ_g) = (3/2)/( 4/3) = 9/8 = 1.125`

Correct Answer is `=>` (D) water, glass, diamond

Q 2828456301

When light passes from air into glass, it experiences change of

(A)

frequency and wavelength

(B)

frequency and speed

(C)

wavelength and speed

(D)

frequency, wavelength and speed

Solution:

Given, ` text()_(a)μ_g = 3/2 , text()_(a)μ_w = 4/3`,

` text()_(w)μ_g = ?`

We know that,

` text()_(w)μ_g = ( text()_(a)μ_g )/( text()_(a)μ_g) = (3/2)/( 4/3) = 9/8 = 1.125`

Correct Answer is `=>` (C) wavelength and speed

Q 2818256109

Which one of the following is the correct arrangement in the
decreasing order of the refractive indices of glass, diamond and
water?

(A)

Glass, water, diamond

(B)

Water, diamond, glass

(C)

Diamond, water, glass

(D)

Diamond. glass, water

Solution:

Given, ` text()_(a)μ_g = 3/2 , text()_(a)μ_w = 4/3`,

` text()_(w)μ_g = ?`

We know that,

` text()_(w)μ_g = ( text()_(a)μ_g )/( text()_(a)μ_g) = (3/2)/( 4/3) = 9/8 = 1.125`

Correct Answer is `=>` (D) Diamond. glass, water

Q 2848156003

Which one of the following diagrams correctly illustrates the
refraction of a normally incident ray of light through a glass slab?

Solution:

Given, ` text()_(a)μ_g = 3/2 , text()_(a)μ_w = 4/3`,

` text()_(w)μ_g = ?`

We know that,

` text()_(w)μ_g = ( text()_(a)μ_g )/( text()_(a)μ_g) = (3/2)/( 4/3) = 9/8 = 1.125`

Correct Answer is `=>` (D)

Q 2868145905

If a man approaches a plane mirror at the rate of 2 km/h, then
his image would approach him at the rate of

(A)

1 km/h

(B)

2 km/h

(C)

4 km/h

(D)

8 km/h

Solution:

`:. v_10 = v_1 - v_0 = -v -v = -2v`

`=- 2 xx 2 = 4 km/h`

[given , `v = 2` km/h ]

Hence, image will approach with
4 km/h.

Correct Answer is `=>` (C) 4 km/h

Q 2838145002

The blue colour of the sky can be
attributed to

(A)

differential scattering of sunlight by the atmosphere

(B)

total internal reflection of the sunlight by the atmosphere

(C)

absorption of sunliqht

(D)

refraction of sunlight by the atmosphere

Solution:

`:. v_10 = v_1 - v_0 = -v -v = -2v`

`=- 2 xx 2 = 4 km/h`

[given , `v = 2` km/h ]

Hence, image will approach with
4 km/h.

Correct Answer is `=>` (A) differential scattering of sunlight by the atmosphere

Q 2888134907

The boundaries of a block of transparent material are found to
be completely invisible when placed in a liquid of refractive
index `mu` . This is possible only, if the refractive index of the
material of the block is

(A)

greater than `mu`

(B)

equal to `mu`

(C)

less than `mu`

(D)

equal to unity

Solution:

`:. v_10 = v_1 - v_0 = -v -v = -2v`

`=- 2 xx 2 = 4 km/h`

[given , `v = 2` km/h ]

Hence, image will approach with
4 km/h.

Correct Answer is `=>` (D) equal to unity

Q 2868134905

The sun is visible to us a little before the actual sunrise and a
little after the actual sunset. This is because of

(A)

refraction

(B)

scattering

(C)

reflection

(D)

diffraction

Solution:

`:. v_10 = v_1 - v_0 = -v -v = -2v`

`=- 2 xx 2 = 4 km/h`

[given , `v = 2` km/h ]

Hence, image will approach with
4 km/h.

Correct Answer is `=>` (A) refraction

Q 2838134902

If a coneave mirror of focal length 10 cm is immersed in water, its
focal length will

(A)

be reduced

(B)

be increased

(C)

remain unchanged

(D)

change sign

Solution:

`:. v_10 = v_1 - v_0 = -v -v = -2v`

`=- 2 xx 2 = 4 km/h`

[given , `v = 2` km/h ]

Hence, image will approach with
4 km/h.

Correct Answer is `=>` (B) be increased

Q 2818034809

The principle of working of periscope is based on

(A)

Only reflection

(B)

Only refraction

(C)

Both reflection and refraction

(D)

Both reflection and interference

Solution:

`:. v_10 = v_1 - v_0 = -v -v = -2v`

`=- 2 xx 2 = 4 km/h`

[given , `v = 2` km/h ]

Hence, image will approach with
4 km/h.

Correct Answer is `=>` (C) Both reflection and refraction

Q 2744512453

If the absolute refractive indices of glass and water are `3/2` and `4/3` respectively, what will be the ratio of velocity of light in glass and water ?
NDA Paper 2 2017

(A)

`3:4`

(B)

`4 : 3`

(C)

`8 : 7`

(D)

`8:9`

Solution:

`:. v_10 = v_1 - v_0 = -v -v = -2v`

`=- 2 xx 2 = 4 km/h`

[given , `v = 2` km/h ]

Hence, image will approach with
4 km/h.

Correct Answer is `=>` (D) `8:9`

Q 2714312250

Which one of the following statements is correct about the magnification, of an optical microscope ?
NDA Paper 2 2017

(A)

Magnification increases with the increase in focal length of eyepiece.

(B)

Magnification increases with the crease in focal length of objective.

(C)

Magnification does. not depend open the focal length of eyepiece.

(D)

Magnification decreases with the increase length of eyepiece.

Solution:

`:. v_10 = v_1 - v_0 = -v -v = -2v`

`=- 2 xx 2 = 4 km/h`

[given , `v = 2` km/h ]

Hence, image will approach with
4 km/h.

Correct Answer is `=>` (D) Magnification decreases with the increase length of eyepiece.

Q 2734212152

Match List t with List II and select the correct answer using the code given below the Lists:

List I(Disease)		List II(Remedy)
(A)	Hypermetropia	(1)	Concave lens
(B)	Presbyopia	(2)	Bifocal lens
(C)	Myopia	(3)	Surgery
(D)	Cataract	(4)	Convex lens

NDA Paper 2 2017

(A)

`A -> 4, B -> 2 , C -> 1, D -> 3`

(B)

`A -> 4, B -> 1 , C -> 2, D -> 3`

(C)

`A -> 3, B -> 1 , C -> 2, D -> 3`

(D)

`A -> 3, B -> 2 , C -> 1, D -> 4`

Solution:

`:. v_10 = v_1 - v_0 = -v -v = -2v`

`=- 2 xx 2 = 4 km/h`

[given , `v = 2` km/h ]

Hence, image will approach with
4 km/h.

Correct Answer is `=>` (A) `A -> 4, B -> 2 , C -> 1, D -> 3`

Q 2714701659

The radii of curvature of the faces of a double convex lens are 10 cm and 20 cm. The refractive index of the glass is `1·5`. What is the power of this lens (in units of dioptre)?
NDA Paper 2 2017

(A)

`+7·5 D`

(B)

` - 7.5 D`

(C)

`+2.5 D`

(D)

`+ 5.0 D`

Solution:

`:. v_10 = v_1 - v_0 = -v -v = -2v`

`=- 2 xx 2 = 4 km/h`

[given , `v = 2` km/h ]

Hence, image will approach with
4 km/h.

Correct Answer is `=>` (A) `+7·5 D`

Q 2743191943

An optical illusion which occurs mainly in deserts during hot summer is based on the principle of ·
NDA Paper 2 2017

(A)

Reflection

(B)

Interference

(C)

Dispersion

(D)

Total internal reflection

Solution:

`:. v_10 = v_1 - v_0 = -v -v = -2v`

`=- 2 xx 2 = 4 km/h`

[given , `v = 2` km/h ]

Hence, image will approach with
4 km/h.

Correct Answer is `=>` (D) Total internal reflection

Q 2316591479

Which one of the following is used to remove astigmatism for a human eye?
NDA Paper 2 2007

(A)

Concave lens

(B)

Convex lens

(C)

Cylinderical lens

(D)

Prismatic lens

Solution:

In astigmatism eye cannot see objects in two
orthogonal directions clearly simultaneously. This object is
removed by using cylinder lens.

Correct Answer is `=>` (C) Cylinderical lens

Q 2316391270

Which one of the following is the most effective carrier of information?
NDA Paper 2 2007

(A)

Cables

(B)

Microwaves

(C)

Radio waves

(D)

Optical fibres

Solution:

Optical fibres also make use of the phenomenon of total internal reflection. In optical fibres losses, secret information like banking, defence etc is more secure because optical signal is confined to the inside of fibre and cannot be tempered easily.

Correct Answer is `=>` (D) Optical fibres

Q 2306180978

The question consists of two statements one labelled as the 'Assertion
(A)' and the other as 'Reason (R.)'. You are to examine these
two statements carefully and select the answers to these
items using the codes given below.
NDA Paper 2 2007

Assertion : A person stands at a distance of 1 m in front of a concave mirror. If the radius of curvature of the mirror is 4 m, the image of the person lies at a distance 2 m behind the mirror.

Reason : The general mirror equation confirms the location of the image from the mirror and it could be a real image.

(A)

Both A and R individually true and R is the correct explanation of A

(B)

Both A and R are individually true but R is not the correct explanation of A

(C)

A is true but R is false

(D)

A is false but R is true

Solution:

For a concave mirror, `f =-R/2=-4/2=-2 m`

`u=-1m`

Using mirror formula

`1/f=1/v+1/u`

`1/(-2)=1/v-1/1`

`=> 1/v=-1/2+1/1=1/2=>v=2m`

As v is positive, hence image formed is virtual and is formed
behind the mirror at 2 m distance.
So, Assertion is true but Reason is false.

Correct Answer is `=>` (C)

Q 2326180971

Assertion : A test tube is filled up with 1/4 of its volume with water and immersed in a glass of water. The upper portion of the test tube looks bright.

Reason : This is due to dispersion of light.

(A)

Both A and R individually true and R is the correct explanation of A

(B)

Both A and R are individually true but R is not the correct explanation of A

(C)

A is true but R is false

(D)

A is false but R is true

Solution:

The upper portion of the test tube looks bright due to total internal reflection of light.

Correct Answer is `=>` (C)

Q 2386080877

Assertion : A test tube is filled up with 1/4 of its volume with water and immersed in a glass of water. The upper portion of the test tube looks bright

Reason : This is due to dispersion of light.

(A)

Both A and R individually true and R is the correct explanation of A

(B)

Both A and R are individually true but R is not the correct explanation of A

(C)

A is true but R is false

(D)

A is false but R is true

Solution:

The upper portion of the test tube looks bright due to total internal reflection of light. So, option (3) is correct.

Correct Answer is `=>` (C)

Q 2376480376

Which one of the following is correct? Large aperture telescopes are used for
NDA Paper 2 2007

(A)

greater resolution

(B)

greater magnification

(C)

reducing lens aberration

(D)

ease of manufacture

Solution:

The resolving power of a telescope, `RP =D/(1.122 lambda)`

where, D is the diameter of the objective lens and 'A. is the
wavelength of light.
So, the telescope should have objective lens of large diameter.

Correct Answer is `=>` (A) greater resolution

Q 2336280172

When light waves travel from air to glass, which
variables are affected?
NDA Paper 2 2007

(A)

Wavelength. frequency and velocity

(B)

Velocity and frequency only

(C)

Wavelength and frequency only

(D)

Wavelength and velocity only

Solution:

When light waves travels from a rarer (air) medium to a
denser (glass), then only frequency of light remains unchanged
but its wavelength and velocity changes.

Correct Answer is `=>` (D) Wavelength and velocity only

Q 2326878771

In a simple microscope, the lens is held at a distance d from the eye and the image is formed at the least distance `(D)` of the distinct vision from the eye; What is the magnifying power of the microscope? where,`f` is the focal length of the lens.
NDA Paper 2 2008

(A)

`D/f`

(B)

`1+(D/f)`

(C)

`1+{(D+f)/f}`

(D)

`1+{(D+d)/f}`

Solution:

The magnifying power of the microscope when the image is formed at the least distance of distinct vision (`D`) is

`M=1+D/f`

Correct Answer is `=>` (B) `1+(D/f)`

Q 2376678576

A far-sighted person has a near point at `100 cm`. What must be the power of the correcting lens?
NDA Paper 2 2008

(A)

`-0.8 D`

(B)

`-3.0 D`

(C)

`+0.8 D`

(D)

`+3.0 D`

Solution:

For a person suffering from far-sightedness,

`u = - 25 cm` and `v = - 100 cm` (near point)

`:. ` `1/f=1/v-1/u=1/(-100)-1/(-25)=-1/100+1/254`

`=(-1+4)/100=3/100`

So, power of correcting lens, `P=100/f D`

`=(100 xx 3)/100=+3 D`

Correct Answer is `=>` (D) `+3.0 D`

Q 2376578476

Consider the following statements
1. The focal length of the objective of a microscope is less than the focal length of the eyepiece.
2. The minimum distance between an object and its real image formed by a convex lens of focal length f is equal to `4 f`.
Which of the statements given above is/are correct?
NDA Paper 2 2008

(A)

Only 1

(B)

Only 2

(C)

Both 1 and 2

(D)

Neither 1 nor 2

Solution:

1. In a compound microscope, an objective of small focal length (`f_0`) with small aperture and as eyepiece of comparatively large focal length(`f` )with larger aperture are used. Therefore, this statement is correct.

2. When object is placed at centre of curvature (`2F`) of convex lens of focal length (`f`), then distance between real image of an object and the object is `4F`. This statement is correct as it is the minimum required distance.

Correct Answer is `=>` (C) Both 1 and 2

Q 2326067871

The sun is visible a little before the actual sunrise because of which one of the following?
NDA Paper 2 2008

(A)

Atmospheric reflection

(B)

Atmospheric dispersion

(C)

Atmospheric diffraction

(D)

Atmospheric refraction

Solution:

The air near the earth is optically denser than that at higher altitude. The sun rays thus travel from rarer to a denser medium. These rays therefore suffers atmospheric refraction. As a result, to an observer the sun appears higher on the horizon than it actually is. Therefore, sun becomes visible a few minutes (about 2 min) before its actual size.

Correct Answer is `=>` (D) Atmospheric refraction

Q 2316767679

If a substance is behaving as convex lens in air and concave lens in water, then which one of the following is its refractive index?
NDA Paper 2 2008

(A)

Smaller than air

(B)

Greater than both air and water

(C)

Greater than air but lesser than water

(D)

Almost equal to water

Solution:

If a substance is behaving as convex lens in air and concave lens in water. then its refractive index is greater than air but lesser than water.

Correct Answer is `=>` (C) Greater than air but lesser than water

Q 2356767674

Consider the following statements The principle of total internal reflection is applicable to explain the
I. formation of image in desert.
2. formation of image in microscope.
3. colour of evening sky.
4. operation of optical fibres.
Which of the statements given above are correct?
NDA Paper 2 2008

(A)

1 and 4

(B)

3 and 4

(C)

2 and 3

(D)

1 and 2

Solution:

The principle of total internal reflection is applicable to
(i) Sparkling or brilliance of diamond.
(ii) Shining of air bubble in water
(iii) Mirage
(iv) Optic pipe and optical fibres.
(v) Working of porro prism.

Correct Answer is `=>` (A) 1 and 4

Q 2356667574

When an optician prescribes a - `5 D` lens, what does it mean?
NDA Paper 2 2008

(A)

Concave lens of 20 cm local length

(B)

Convex lens of 20 crn focal length

(C)

Concave lens of 5 crn focal length

(D)

Convex lens of 5 crn focal length

Solution:

Power of a lens,`P =1/f`

here, `P=-5 D`

`:. -5 =100/f` cm

or `f=-20` cm

The negative sign indicates that it is a concave lens.

Correct Answer is `=>` (A) Concave lens of 20 cm local length

Q 2326567471

Which of the following statements is/are true regarding a light wave travelling from air to glass?
1. Its frequency remains unchanged.
2. Its speed changes.
Select the correct answer using the codes given below
NDA Paper 2 2008

(A)

Only 1

(B)

Only 2

(C)

Both 1 and 2

(D)

Neither 1 nor 2

Solution:

When a light wave moves from air to glass, its wavelength changes but its frequency remains the same. As the wavelength of light wave decreases when it enters a denser medium (glass) from a raser medium (air), its speed also decreases.

Correct Answer is `=>` (B) Only 2

Q 2326056871

A ray of light is incident normally on .one of the faces of right angled isosceles prism as shown above. It undergoes total internal reflection from hypotenuse. Which one of the following is the minimum refractive index of the material of the prism?
NDA Paper 2 2008

(A)

1.0

(B)

1.33

(C)

1.414

(D)

1.6

Solution:

The given situation is shown in fig

Here,` i = C` (critical angle) `= 45°`

For the condition of total internal reflection,

`mu=1/(sin C)=1/(sin 45^o)`

`=1/(1//sqrt2)=sqrt 2=1.414`

Correct Answer is `=>` (C) 1.414

Q 2316834770

How far must a girl stand in front of a concave spherical mirror of radius `120` cm to see an erect image of her face four times its natural size?
NDA Paper 2 2009

(A)

40 cm from the mirror

(B)

45 cm from the mirror

(C)

50 cm from the mirror

(D)

55 cm from the mirror

Solution:

For erect image of girl's face

`m=+4`

`m=t/(t+4)`

`:. +4=(-60)/(-60-u)`

`=> u=-45` cm

Correct Answer is `=>` (B) 45 cm from the mirror

Q 2386812777

Different objects at different distances are seen by the eye. The parameter that remains constant is the
NDA Paper 2 2010

(A)

focal length of the eye lens

(B)

object distance from the eye lens

(C)

radii of curvature of the eye lens

(D)

image distance from the eye lens

Solution:

Focal length of the optical instrument is its characteristic property. Hence, the focal length of the eye lens remains constant.

Correct Answer is `=>` (A) focal length of the eye lens

Q 2346812773

An object is placed at a distance of `12 cm` from a convex lens on its principal axis and a virtual image of certain size is formed. If the object is moved further `8 cm` away from the lens, a real image of the same size as that of the virtual image is formed. Which one of the following is the focal length of the lens?
NDA Paper 2 2010

(A)

`15 cm`

(B)

`16 cm`

(C)

`18 cm`

(D)

`20 cm`

Solution:

If f be the focal length of the lens and n the magnitude
of magnification.

Case I : When the image is virtual

`u=-12=>v=-12 n`

`1/v-1/u=1/f=>1/(-12 n)+1/12=1/f`

`1-1/n=12/f`

Case II: When the image is real

`U=-(8+12)=-20`

`v =20 n`

`1/(+20 n)+1/20=1/f=> 1+1/n=20/f`

From Eqs. (i) and (ii),

`2=12/f+20/f=32/f=> 2=32/f`

`f=32/2=16 cm`

Correct Answer is `=>` (B) `16 cm`

Q 2316101079

What is the telescope designed to search for earth-size planets in the nearby region of our galaxy, termed as?
NDA Paper 2 2009

(A)

Hubble telescope

(B)

Kepler telescope

(C)

Copernicus telescope

(D)

Newton telescope

Solution:

It is the Hubble's telescope which is designed so that we can search for earth-size planets in the near by region of our galaxy.

Correct Answer is `=>` (A) Hubble telescope

Q 2325191961

An object is kept `5` cm in front of a concave mirror of focal length `15` cm. What will be the nature of the image?
NDA Paper 2 2009

(A)

Virtual, not magnified

(B)

Virtual, magnified

(C)

Real, not magnified

(D)

Real, magnified

Solution:

When object is placed between F and P, then its virtual, erect and large (magnified) image is formed

Correct Answer is `=>` (B) Virtual, magnified

Q 2385178967

A coin in a beaker filled with water appears raised. This phenomenon occurs because of the property of
NDA Paper 2 2010

(A)

reflection of light

(B)

refraction of light

(C)

total internal reflection of light

(D)

interference of light

Solution:

The coin appears to be raised from its actual position due to refraction of light. The apparent depth of the coin is less than its real depth in water. The real depth and apparent depth are related to each other as
`(text(Real depth))/(text(Apparent depth))=eta` (refractive index)

Correct Answer is `=>` (B) refraction of light

Q 2335178962

The radius of curvature of a plane mirror
NDA Paper 2 2010

(A)

is zero

(B)

is infinity

(C)

can be anywhere between zero and infinity

(D)

None of the above

Solution:

Focal length of a plane mirror is infinite, hence the radius of curvature, `R=2f=oo` (infinite)

Correct Answer is `=>` (B) is infinity

Q 2345478363

If an object is placed at the centre of curvature of
a concave mirror, the position of the image is
NDA Paper 2 2010

(A)

at the principal focus

(B)

between the principal focus and the centre of curvature

(C)

at the centre of curvature

(D)

beyond the centre of curvature

Solution:

Image formation by a concave mirror
When object is placed at the centre of curvature.

The image formed is real. inverted and of same size and position
of image is at centre of curvature.

Correct Answer is `=>` (C) at the centre of curvature

Q 2325067861

The ratio of the focal length of the objective to the focal length of the eyepiece is greater than one for
NDA Paper 2 2010

(A)

a microscope

(B)

a telescope

(C)

both microscope and telescope

(D)

neither microscope nor telescope

Solution:

Microscope A microscope is an optical instrument to see small objects as magnified one. It consists of a convex lens of small focal length. Telescope Telescope is an optical instrument to clearly observe the distant objects. It consists of two convex lenses, an objective lens of larger focal length `(f_0)` and an eyepiece of small focal length `(f_a).` So, `f_0 > f_a`· According to the question, for a telescope `f_0/(f_a) > f`

Correct Answer is `=>` (A) a microscope

Q 2365345265

Which one of the following four glass lenses is a diverging lens?
NDA Paper 2 2010

Solution:

Diverging lens is the lens having both spherical surfaces or one spherical and other plane surface such that it is thin in the middle and thick at the edges. In the given figure option (1) represents a convex-concave lens which is a diverging lens.

Correct Answer is `=>` (A)

Q 2335345262

Which one of the following is the correct angle between the incident and reflected rays when a ray of light incident normally on a plane mirror'?
NDA Paper 2 2010

(A)

`180^o`

(B)

`90^o`

(C)

`45^o`

(D)

`0^o`

Solution:

When a ray of light is incident normally on a plane mirror, then the ray of light will retrace its path. Since, the incident ray and reflected rays both are along the normal to the plane.

Correct Answer is `=>` (D) `0^o`

Q 2385245167

The stars seem to be higher on the sky than they actually are. This can be explained by.
NDA Paper 2 2011

(A)

atmospheric refraction

(B)

dispersion of light

(C)

total internal reflection

(D)

diffraction of light

Solution:

When light travels from one medium to another medium refraction takes place. Light emitted by stars passes through the atmosphere of earth before reaching our eyes. The atmosphere of the earth is not uniform but consists of many layers of different densities. The layers close to the surface of earth are optically denser and as we go higher the density and refractive index decreases progressively. The light coming from stars suffers refraction and every time it bends towards the normal. So due to atmospheric refraction, the apparent position of the star is different from the actual position of the star.

Correct Answer is `=>` (A) atmospheric refraction

Q 2325245161

A spherical air bubble is embedded in a piece of glass. For a ray of light passing through the bubble, it behaves like a
NDA Paper 2 2011

(A)

converging lens

(B)

diverging lens

(C)

plano-converging lens

(D)

plano-diverging lens

Solution:

A spherical air bubble in a piece of glass behaves like as diverging lens, because refractive index of air is less than the refractive index of glass.

Correct Answer is `=>` (B) diverging lens

Q 2355134964

When a ray of light is going from one medium to another its.
NDA Paper 2 2011

(A)

wavelength remains same

(B)

frequency remains same

(C)

frequency increases

(D)

wavelength increases

Solution:

When light passes from one medium to another medium, speed of light changes but frequency of light remains unchanged.

Correct Answer is `=>` (B) frequency remains same

Q 2375623566

Light travels slower in glass than in air because
NDA Paper 2 2011

(A)

refractive index of air is less than that of glass

(B)

refractive index of air is greater than that of glass

(C)

density of glass is greater than that of air

(D)

density of glass is less than that of air

Solution:

The speed of light depends on the nature of the
medium in which it travels. The speed of light in a medium is
related to its refractive index by the relation.

Refractive index of medium

`eta= (text(Speed of light in vacuum (C))/(text(Speed of light in that medium (v))`

`eta=c/v`

Since, c is fixed, the speed of light is any mediurn decreases with increase in refractive index. The refractive index of air is less than that of glass.

Correct Answer is `=>` (A) refractive index of air is less than that of glass

Q 2325623561

Suppose you are standing 1 m in front of a plane mirror. What should be the minimum vertical size of the mirror so that you can see your full image in it?
NDA Paper 2 2011

(A)

0.50 m

(B)

2 m

(C)

Half of your height

(D)

Twice your height

Solution:

The length of the plane mirror to have the full length
image of a person standing in front of it is equal to half the height
of the person. For example, the full length image of a person of
height `160` crn can be produced by a plane mirror of `1/2 xx 160` crn

`= 80` crn.

Correct Answer is `=>` (C) Half of your height

Q 2385523467

which one among the following is the major cause of blurring and unsharp images of objects observed through very large telescope at the extreme limit of magnification'?
NDA Paper 2 2011

(A)

Air turbulence of earth's atmosphere

(B)

Poor optical polish achievable on large mirrors

(C)

Poor tracking capacities of telescopes

(D)

Varying density of air in the Earth's atmosphere

Solution:

The major cause of blurring and unsharp images of objects observed through a very large telescope at tile extreme limit of magnification is air turbulence of earth's atmosphere

Correct Answer is `=>` (A) Air turbulence of earth's atmosphere

Q 2355523464

Light travels in optical fibre irrespective of its shape because it is a device by which signals can be transferred from one location to another. It is based on the phenomenon of.
NDA Paper 2 2011

(A)

diffraction of light

(B)

refraction of light

(C)

polarisation of light

(D)

total internal reflection of light

Solution:

The optical fibres are used to transmit light signals from one place to another without any practical loss in the intensity of light signal. It works on the principle of total internal reflection.

Correct Answer is `=>` (D) total internal reflection of light

Q 2335523462

Which one among the following statements is correct'?
NDA Paper 2 2011

(A)

Convex mirrors are used by doctors to examine oral cavity

(B)

Concave mirrors are used as reflectors

(C)

Convex mirrors are used as reflectors

(D)

Convex mirrors should be used for shaving

Solution:

Concave mirrors are used by dentists to focus light on the tooth to be examined. Concave mirrors are also used as reflectors in the head lights of cars, search lights etc. Concave mirrors are used as shaving mirrors and as make up mirrors to see enlaroed erect image of the face. Convex mirror are used as rear-view mirrors or side mirrors on automobiles.

Correct Answer is `=>` (B) Concave mirrors are used as reflectors

Q 2304391258

What is the power of the lens, if the far point of a short-sighted eye is `200 cm`?
NDA Paper 2 2011

(A)

`-0.5` D

(B)

`2` D

(C)

`1` D

(D)

`-1.5` D

Solution:

For short sighted eye concave lens is used and focal
length of used lens `F = -d` (defected for point)

`:.` Power, `P =-1/(200 cm)=-1/(2 m)=-0.5 D`

Correct Answer is `=>` (A) `-0.5` D

Q 2384291157

A one-rupee coin is placed at the bottom of a vessel. Water is then poured into the vessel such that the depth of water becomes `20` cm. If water has refractive index `4/3`, the coin would be seen at a depth of
NDA Paper 2 2011

(A)

`20` cm

(B)

about `26` cm

(C)

`15` cm

(D)

`25` cm

Solution:

Apparent depth

`(h')=(text(Real depth)(h))/(text(Refractive index of the medium)( eta))`

`=20/(4/3)=15` cm

Correct Answer is `=>` (C) `15` cm

Q 2374291156

Refractive index of an optical medium changes with
1. the nature of the medium.
2. the change is the angle of incidence of the ray.
3. colour of the incident ray.

Select the cotnct answer using the codes given below
NDA Paper 2 2012

(A)

1 and 3

(B)

2 and 3

(C)

1 and 2

(D)

All of these

Solution:

Ray of light has different velocities in different media. Angle of incidence of the ray also affects the view through the medium. Ray of light contains seven colours of different wavelengths which gives a unique view each time when seeing from different depths.

Correct Answer is `=>` (D) All of these

Q 2364191055

The image formed by a convex mirror of a real object is larger than the object
NDA Paper 2 2012

(A)

when `u < 2f`

(B)

when `u > 2f`

(C)

for all values of ` u`

(D)

for no values of `u`

Solution:

A convex mirror gives only virtual, erect and smaller image, whatever may be the position of the object in front of the mirror.

Correct Answer is `=>` (D) for no values of `u`

Q 2344880753

Two thin convex lenses of focal lengths `4 cm` and `8 cm` are separated by a distance of `4 cm` in air. The combination will have the focal
NDA Paper 2 2012

(A)

`4` cm

(B)

`8` cm

(C)

`12` cm

(D)

`32` cm

Solution:

We know that

`1/f=(1/f_1)+(1/f_2) -x/(f_1f_2)`

where, `t_1 = 4` cm

`f_2 = 8` cm, `x = 4` cm

Focal length `= 4.5` cm= `4` cm

Correct Answer is `=>` (A) `4` cm

Q 2364680555

If the focal length of the biconvex lens is `25 cm`, then the power of the lens will be
NDA Paper 2 2012

(A)

`+4 D`

(B)

`-4 D`

(C)

`+0.04 D`

(D)

`+0.004 D`

Solution:

We know that,

`P=1/(l(meter))=1/(25 xx 10^(-2))=4D`

Correct Answer is `=>` (A) `+4 D`

Q 2384480357

To obtain the powerful parallel beams of light
from a vehicle's headlight, one must use
NDA Paper 2 2012

(A)

front surface silvered plane mirror

(B)

back surface silvered plane mirror

(C)

concave mirror

(D)

convex mirror

Solution:

Convex mirrors are not used in car head lights but
concave ones as they form a parallel and powerful beam of light
focusing on a particular area. Convex mirror (if used in
headlights) diverge the rays over a large area hence are more
used in street lights.

Correct Answer is `=>` (C) concave mirror

Q 2344367253

A refracting telescope consists of
NDA Paper 2 2012

(A)

one concave mirror and one convex lens

(B)

two convex lenses of equal focal length

(C)

two concave mirrors of different focal lengths

(D)

two convex lenses of unequal focal lengths

Solution:

A refracting telescope works just like a magnifying glass. It uses a convex glass lens to bend light and bring it into focus. This lens is thicker in the centre than it is forward its edges, which bends the light more at the edge of the lens than light coming through the centre. This allows all of the light to come together at a focus point The point of focus is where the image is created

Correct Answer is `=>` (D) two convex lenses of unequal focal lengths

Q 2354145954

The mirror used for the head light of a car is
NDA Paper 2 2012

(A)

spherical concave

(B)

plane

(C)

cylindrical

(D)

parabolic concave

Solution:

Concave mirrors are used because they will reflect a light source inside the curve in one general direction. To be more specific, the mirrors are close to parabolic. Parabolas have the property that light beams generated at the focal point of the parabola are all reflected parallel out of the mirror.

Correct Answer is `=>` (D) parabolic concave

Q 2334534452

The spread in colors in a rainbow on sky is primarily due to.
NDA Paper 2 2013

(A)

dispersion of sunlight

(B)

reflection of sunlight

(C)

refraction of sunlight

(D)

total internal reflection of sunligllt

Solution:

A rainbow is an optical and meteorological phenomenon that is caused by reflection of light in water, droplets in the Earth's atmosphere, resulting in a spectrum of light appearing in the sky. It takes the form of a multicolored are rainbow caused by sunlight always appear in the section of sky directly opposite the Sun.

Correct Answer is `=>` (B) reflection of sunlight

Q 2384134057

An optician prescribes a power `=- 0.5` diopter. The corresponding lens must be a.
NDA Paper 2 2013

(A)

convex lens of focal length `2 rn`

(B)

convex lens of focal length `50 cm`

(C)

concave lens of focal length `2 m`

(D)

concave lens of focal length `50 crn`

Solution:

It is given that `P =- 0. 5` dioptre

`F=1/P=1/(-0.5)=-2 m`

Negative sign shows concave lens. It means it is a concave lens
of focal length `2m`.

Correct Answer is `=>` (C) concave lens of focal length `2 m`

Q 2344123953

An object is placed at the focus of a concave mirror. The image will be.
NDA Paper 2 2013

(A)

real, inverted, same size at the focus

(B)

real, upright, same size at the focus

(C)

virtual, inverted, highly enlarged at infinity

(D)

real, inverted. highly enlarged at infinity

Solution:

The object is placed at title focus of a concave mirror.
The image will be real, inverted and highly enlarged at infinity.

Correct Answer is `=>` (D) real, inverted. highly enlarged at infinity

Q 2354123054

The human eye is like a camera and hence, it contains a system of lens. The eye lens forms
NDA Paper 2 2013

(A)

a straight or upright, real image of the object on the retina

(B)

an inverted, virtual image of the object on the retina

(C)

an inverted, real image of the object on the retina

(D)

a straight or upright, real image of the object on the iris

Solution:

The eye lens forms an inverted, real image of the object
on the retina.

Correct Answer is `=>` (C) an inverted, real image of the object on the retina

Q 2313691540

White light while passing through a glass prism breaks up into light of different colours because
NDA Paper 2 2013

(A)

refractive index of glass for different colours of light is different

(B)

glass prism absorbs white light and emits lights of several colours in different directions

(C)

of total internal reflection of white light on surfaces of the prism

(D)

of the interference of different colours inside the prism

Solution:

White light while passing through a glass prisms
breaks-up into light of different colours because refractive index
of glass for different colours of light is different.

Correct Answer is `=>` (A) refractive index of glass for different colours of light is different

Q 2363591445

Rays of light get refracted while passing from air to glass because
NDA Paper 2 2013

(A)

clensity of glass is higher than that of air

(B)

they cannot be reflected from a glass surface

(C)

glass absorbs energy from the light rays

(D)

speed of light in glass is less than the speed of light in air

Solution:

Rays of light get refracted while passing from air to
glass because density of glass is higher than that of air refraction
is the change in direction of a wave due to change in its
transmission medium.

Correct Answer is `=>` (A) clensity of glass is higher than that of air

Q 2343678543

During sunrise and sunset, sun appears reddishorange, because
NDA Paper 2 2013

(A)

during that time sun emits only reddish-orange light

(B)

all other colours are absorbed by the atmosphere

(C)

reddish-orange light is least scattered by the atmosphere

(D)

all other colours apart from reddish-orange are reflected back by the atmosphere

Solution:

During sunrise and sunset, sun appears reddish-orange because reddish-orange light is least scattered by the atmosphere.

Correct Answer is `=>` (C) reddish-orange light is least scattered by the atmosphere

Q 2353067844

A beautiful rainbow on the sky is due to the
NDA Paper 2 2013

(A)

dispersion of sunlight from a wate droplet only

(B)

reflection of sunlight from a wate droplet only

(C)

reflection and rel'raction of sunlight from a water droplet only

(D)

refraction, dispersion and reflection of sunlight from a water droplet

Solution:

The formation of a rainbow involves a series of physical
phenomena- reflection, refraction, dispersion and total internal
reflection.

Correct Answer is `=>` (D) refraction, dispersion and reflection of sunlight from a water droplet

Q 2189601517

A pencil is placed upright at a distance `10 cm` from a convex lens of focal length `15 cm`. The nature of the image of the pencil will be.
NDA Paper 2 2016

(A)

real, inverted and magnified

(B)

real, erect and magnified

(C)

virtual, erect and reduced

(D)

virtual, erect and magnified

Solution:

It is given that,

Focal length of the convex lens, `f = 15 cm`

Distance of pencil from the pole, `u = -10 cm`

Applying mirror formula, we get

`1/v + 1/u = 1/f => 1/v -1/10 =1/15`

`=> 1/v = 1/10 +1/15 = 25/150 => v = 6 cm`

`:.` Magnification, `m = - v/u = (-6)/-10 = 0.6`

As magnification is positive and less than one image

will be vertucal, erect and diminished.

Correct Answer is `=>` (C) virtual, erect and reduced

Q 2139601512

An object is placed at the centre of curvature of a concave mirror of focal length `16 cm`. If the object is shifted by `8 cm` towards the focus, the nature of the image would be
NDA Paper 2 2016

(A)

real and magnified

(B)

virtual and magnified

(C)

real and reduced

(D)

virtual and reduced

Solution:

Focal length of the concave mirror, `f = -16 cm`

`:.` Magnitude of radius of curvature of the mirror,

`|R| = 2f = 32cm`

When object is shifted towards the focus, new distance
of the object

`u =- (32- 8) cm=- 24 cm`

Applying mirror formula, we get

`1/v + 1/u = 1/f`

`=> 1/v - 1/24 = 1/-16`

` =>1/v = 1/24 - 1/16 = (16 - 24)/(24 xx 16) = (-8)/(24 xx 16)`

` => u = - 48 cm`

`:.` Magnification, `m = - v/u = (-(-48))/-24 = -2`

As magnification is negative and having magnitude more than one, image will be real and magnified.

Correct Answer is `=>` (A) real and magnified

Q 2118523409

A lady is standing in front of a plane mirror at a distance of `1 m ` from it. She walks `60 cm` towards the mirror. The distance of her image now from herself (ignoring the thickness of the mirror) is
NDA Paper 2 2016

(A)

`40 cm`

(B)

`60 cm`

(C)

`80 cm`

(D)

`120 cm`

Solution:

Initial distance of the lady from the mirror is

` x_(1) = 1 m = 100 cm`

After moving `60 cm` towards the mirror, new

distance is `x_(2) = 100 - 60 = 40 cm`

`:.` Distance of her image from herself is

`d = x_(2) + x_(2) = 2x_(2) = 80 cm`

Correct Answer is `=>` (C) `80 cm`

Q 1659201114