## Ray Optics Questions and Answers

Question 1 |

A convex lens is dipped in a liquid whose refractive index is equal to the refractive index of the lens. Then its focal length will

Remain unchanged | |

Become zero | |

Become small, but non–zero | |

Become infinite |

Question 2 |

Line spectrum was first of all theoretically explained by

Fraunhofer | |

Bohr | |

Swan | |

Kirchoff |

Question 3 |

The fine powder of a coloured glass is seen as

Black | |

Coloured | |

That of the glass colour | |

White |

Question 4 |

When a plane mirror is placed horizontally on a level ground at a distance of 60 m from the foot of a tower, the top of the tower and its image in the mirror subtend an angle of 90

^{o}at the eye. The height of the tower will be90 m | |

60 m | |

30 m | |

120 m |

Question 5 |

A lamp is hanging at a height of 4

*m*above a table. The lamp is lowered by 1*m*. The percentage increase in illuminace will be64% | |

92% | |

40 % | |

78% |

Question 6 |

Line spectrum contains information about

The atoms as well as molecules of the source | |

The atoms of the prism | |

The molecules of the source | |

The atoms of the source |

Question 7 |

A lamp is hanging at a height 40

*cm*from the centre of a table. If its height is increased by 10*cm*the illuminance on the table will decrease by20% | |

36% | |

27% | |

10 % |

Question 8 |

In order to obtain a real image of magnification 2 using a converging lens of focal length 20

*cm*, where should an object be placed50 cm | |

30 cm | |

– 30 cm | |

– 50 cm |

Question 9 |

Colour of the sky is blue due to

None of these | |

Total emission | |

Scattering of light | |

Total internal reflection |

Question 10 |

A neon sign does not produce

An absorption spectrum | |

Photons | |

An emission spectrum | |

Line spectrum |

Question 11 |

The radius of curvature of convex surface of a thin plano-convex lens is 15

*cm*and refractive index of its material is 1.6. The power of the lens will be–2D | |

+1 D | |

+4 D | |

+3 D |

Question 12 |

The length of a telescope is 36

*cm*. The focal lengths of its lenses can be30 cm, – 6 cm | |

– 30 cm, 6 cm | |

– 30 cm, – 6 cm | |

30 cm, 6 cm |

Question 13 |

The number of wavelengths in the visible spectrum

2000 | |

6000 | |

Infinite | |

4000 |

Question 14 |

For a normal eye, the least distance of distinct vision is

0.50 m | |

Infinite | |

25 m | |

0.25 m |

Question 15 |

Chromatic aberration of lens can be corrected by

Reducing its aperature | |

Proper polishing of its two surfaces | |

Providing different suitable curvature to its two surfaces | |

Suitably combining it with another lens |

Question 16 |

The magnifying power of a simple microscope can be increased, if we use eye-piece of

Higher focal length | |

Smaller focal length | |

Higher diameter | |

Smaller diameter |

Question 17 |

Under minimum deviation condition in a prism, if a ray is incident at an angle 30

^{o}, the angle between the emergent ray and the second refracting surface of the prism is0° | |

60° | |

45° | |

30° |

Question 18 |

In a compound microscope cross-wires are fixed at the point

Where the focal point of the eye-piece lies | |

Where the image is formed by the objective | |

Where the image is formed by the eye-piece | |

Where the focal point of the objective lies |

Question 19 |

A thin equiconvex lens is made of glass of refractive index 1.5 and its focal length is 0.2

*m*, if it acts as a concave lens of 0.5*m*focal length when dipped in a liquid, the refractive index of the liquid is**Related:** West Bengal JEE Physics Sample Paper

13/8 | |

15/8 | |

17/8 | |

9/8 |

Question 20 |

A symmetric double convex lens is cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4

*D*, the power of a cut lens will be4 D | |

3 D | |

5 D | |

2 D |

Question 21 |

A converging lens is used to form an image on a screen. When upper half of the lens is covered by an opaque screen

Complete image will be formed of same intensity | |

Half the image will disappear | |

Half image will be formed of same intensity | |

Complete image will be formed of decreased intensity |

Question 22 |

Relative difference of focal lengths of objective and eye lens in the microscope and telescope is given as

It is more in telescope | |

It is equal in both | |

It may be more in any one | |

It is more in microscope |

Question 23 |

On which of the following does the magnifying power of a telescope depends

The diameter of aperture of the objective and that of the eye piece | |

The focal length of the objective and that of the eye piece | |

The diameter of aperture of the objective only | |

The focal length of the objective only |

Question 24 |

The dispersive powers of glasses of lenses used in an achromatic pair are in the ratio 5 : 3. If the focal length of the concave lens is 15

*cm*, then the nature and focal length of the other lens would beConcave, 25 cm | |

Convex, 25 cm | |

Concave, 9 cm | |

Convex, 9 cm |

Question 25 |

An object has image thrice of its original size when kept at 8

*cm*and 16*cm*from a convex lens. Focal length of the lens is16 cm | |

Between 8 cm and 16 cm | |

8 cm | |

Less than 8 cm |

Question 26 |

An eye specialist prescribes spectacles having a combination of convex lens of focal length 40

*cm*in contact with a concave lens of focal length 25*cm*. The power of this lens combination in diopters is– 1.5 | |

– 6.67 | |

+ 1.5 | |

+ 6.67 |

Question 27 |

The critical angle for diamond (refractive index = 2) is

60° | |

About 20° | |

30° | |

45° |

Question 28 |

A convex lens, a glass slab, a glass prism and a solid sphere all are made of the same glass, the dispersive power will be

Only in prism | |

In all the four | |

In the lens and solid sphere | |

In the glass slab and prism |

Question 29 |

If refractive index of red, violet and yellow lights are 1.42, 1.62 and 1.50 respectively for a medium. Its dispersive power will be

0.3 | |

0.4 | |

0.1 | |

0.2 |

Question 30 |

An imaginary line joining the optical centre of the eye lens and the yellow point is called as

Neutral axis | |

Vision axis | |

Principal axis | |

Optical axis |

Question 31 |

Five

*lumen/watt*is the luminous efficiency of a lamp and its luminous intensity is 35*candela*. The power of the lamp is176 W | |

80 W | |

88 W | |

36 W |

Question 32 |

Ability of the eye to see objects at all distances is called

Hypermetropia | |

Myopia | |

Accommodation | |

Binocular vision |

Question 33 |

Which source is associated with a line emission spectrum?

Neon street sign | |

Sun | |

Electric fire | |

Red traffic light |

Question 34 |

A compound microscope has two lenses. The magnifying power of one is 5 and the combined magnifying power is 100. The magnifying power of the other lens is

**Related:** JEE Mathematics Question Bank

20 | |

50 | |

10 | |

25 |

Question 35 |

Retina of eye acts like ........ of camera

None of these | |

Shutter | |

Film | |

Lens |

There are 35 questions to complete.

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