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ECAT Physics Lights and Optics Online Test

Maan AliLast Updated: April 18, 2025

Physics Lights and Optics MCQS Online Test

ECAT Physics Lights and Optics Chapter Online Test

Total Questions:	88
Time Allowed:	40 Minutes
Total Marks:	88
How to Attempt Test:	Please choose the right Option in MCQ-type question.
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Physics Lights and Optics Chapter Online Test

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Page 1 of 4

Physics

1. In a plane polarized light

No vibration at all

Vibration take place in a direction perpendicular to the direction of propagation of light

Vibration in two mutually perpendicular directions

Vibration in all direction

2. The splitting of white light into several colors on passing through a glass prism is due to

Diffraction

Refraction

Reflection

Interference

3. Which of the following frequency ranges includes most of the electromagnetic waves emitted by the ultra – violet tubes used in a sun bed?

5 x 10¹¹ to 5 x 10¹⁴ Hz

5 x 10⁵ to 5 x 10⁵ Hz

5 x 10¹⁴ to 5 x 10¹⁷ Hz

5 x 10⁵ to 5 x 10¹¹ Hz

4. Every point of a wave front may be considered as a

Source of secondary wave front

Source of wave front

None of these

Source

5. When crest of one wave falls over the trough of the other wave this phenomenon is known as

Diffraction

Destructive interference

Polarization

Constructive interference

6. A thin film is a transparent medium whose thickness with the wavelength of light are

Comparable

Not comparable

Both

None of these

7. Wave front is the locus of all points in vibration are in the same

Wavelength

Phase

Frequency

All of these

8. Who devise the experimental arrangement is 1801 for studying interference effects of light?

Young

Newton

Huygen

None of these

9. When the light is incident on polarizing angle which of the following is completely polarized?

Both reflected and refracted light

Reflected light

Neither reflected nor refracted light

Refracted light

10. Interference was observed in interference chamber, when air was present, now the chamber is evacuated and if the same light is used, a careful observer will see

Interference with bright bands

Interference in which breadth of the fringe will be slightly increase

Interference with dark bands

No interference

11. The cause of mirage observed in desert is

Total internal reflection

Scattering

Refraction

Reflection

12. The locus of all points in the same phase of vibration is called:

Wave number

Wavelength

Wave front

Wave form

13. If a wave can be polarized, it must be

A longitudinal wave

A sound wave

A transverse waves

An electromagnetic wave

14. Light is a type of energy which produces sensation of

Sound

Vision

None of these

Feeling

15. The relation of constructive interference in X-ray diffraction is called

Huygen’s formula

Compton effect

Laue’s pattern

Bragg’s law

16. The light produced by a laser is all the following except

Incoherent

Electromagnetic

Monochromatic

In the form of a narrow beam

17. The idea of light as wave produced by

Huygen

Michelson

Newton

Thomos young

18. A polarizer is used to

Reduced intensity of light

Produce unpolarised light

Produce polarized light

Increase intensity of light

19. The condition for the bright fringes formed due to constructive interference in a diffraction grating is:

md cos θ = λ

d sin θ = m/2 λ

d sin θ = 2λm

d sin θ = mλ

20. For constructive interference the path difference is

Mλ

m²λ

½ mλ

(m – 1)λ

21. The locus of all points in a medium having the same phase of vibration is called

Wave front

Trough

Crest

Wavelength

22. Huygen’s wave fronts which sends out secondary wavelets with a speed equal to

Speed of propagation of the wave

Speed of propagation greater than wave

Speed of propagation less than the wave

B and C

23. Which one of the following phenomena is not explained by Hygen’s construction of wave front?

Reflection

Diffraction

Refraction

Origin of spectra

24. Why laser rays are used to measure long distance?

Laser rays are most coherent waves

Laser rays are high velocity waves

Laser rays propagate in a straight line

Laser rays are not absorbed

25. To demonstrate the phenomenon of interference we require two sources that emit radiation

Different wavelength

Of nearly the same frequency

Of the same frequency and having definite phase relationship

Of same frequency

Page 2 of 4

26. Ray optics is valid, when characteristic dimensions are

Much smaller than the wavelength of length

Much larger than the wavelength of light

Of the order of one millimeter

Of the same order as the wavelength of light

27. In Young double slit experiment, if white light is used

Colored fringes will be seen

No interference fringes will be seen

Alternate dark and bright fringes will be seen

Impossible to predict

28. In the phenomenon of interference, the bright ad dark fringes are of

Equal width

Different width

None of these

Dark fringes are thicker than bright

29. Which of the following is conserved when light waves interfere?

Momentum

Intensity

Amplitude

Energy

30. If a source of light is moving away from stationary observer, then frequency of light wave appears to change because of

Doppler’s effect

Diffraction

None of these

Interference

31. The phenomenon of bending of light waves around the edges of an obstacle or a narrow opening is called.

Reflection

Refraction

Transmission

Diffraction

32. On a rainy day, if there is an oil drop on tar road, colored rings are seen around this drop. This is because of

Interference pattern produced due to thin oil film

Total internal reflection of light

Polarization

Diffraction pattern

33. In Huygen’s wave theory, the locus of all points in the same state of vibration is called

A half-period zone

A ray

Wave front

Vibrator

34. Fraunhoffer’s lines commonly visible in the sun’s spectrum are examples of

Line absorption spectrum

Band emission spectrum

Band absorption spectrum

Line emission spectrum

35. In Young’s experiment, a dark fringe is observed when:

2π Sin θ = (m + 1/2)λ

m Sin θ = (d + 1/2)λ

d Sin θ = (m + 1/2)λ

½ d Sin θ = mλ

36. Diffraction effect is

Less for a round edge

Less for a sharp edge

More for a round edge

More for a sharp edge

37. The light produced by a laser is all the following except

Incoherent

Electromagnetic

In the form of a narrow beam

Monochromatic

38. A spectrum which contains all wavelengths without any break is called

Continuous emission spectrum

All of these

Emission spectrum

Line spectrum

39. A prism splits a beam of white light into its seven constituent colors. This is so because

Amplitude of different colors is different

Velocity of different colors is different

Phase of different colors is different

Energy of different colors is different

40. In Michelson interferometer to switch the fringe from bright to dark the mirror should be displaced through

?/4

?/3

?/6

?/2

41. The contrast in the fringes in any interference pattern depends on

Distance between the slits

Intensity ratio of the sources

Wavelength

Fringe width

42. Choose the correct statement

Rays are not normal to wave front

Rays may be normal to wave front

There is no relationship between rays and wave fronts

Rays are normal to wave front

43. According to Huygen, every point on a wave front may be regarded as a __________ of secondary wavelets.

Producer

Source

Base

Origin

44. A point source of light placed in a homogeneous medium gives rise to

A spherical wave front

A plane wave front

An elliptical wave front

A cylindrical wave front

45. The condition for constructive interference of two coherent beams is that the path difference should be

Integral multiple of λ/2

Odd integral multiple of λ/2

Integral multiple of λ

Even integral multiple of λ

46. When the two surfaces of a thin film are parallel and the light is incident at a certain angle, _________ fringes are formed.

Circular

Parabolic

Elliptical

Straight

47. Light on passing through a Polaroid is

Circularly polarized

Elliptically polarized

Plane polarized

Un-polarized

48. Which effect provides direct experimental evidence that light is a transverse, rather than a longitudinal, wave motion?

The intensity of light from a point source falls off inversely as the square of the distance from the source

Light can be polarized

Two coherent light waves can be made to interfere

Light can be diffracted

49. Which of the following properties show light is transverse wave in nature?

Polarization

Interference

Diffraction

Reflection

50. Central spot of New tons rings

Dark

Dart for large wavelength

Bright for large wavelength

Bright

Page 3 of 4

51. If the dark fringe is to be observed then we have relation

Y = (m + 1/2) λL/d

Y = (m + 1/2) λd/L

Y = (m + 1) λL/d

Y = (m + ½) dL/λ

52. A diffraction grating has 500 lines per mm. Its slit spacing or grating element will be equal to

2 x 10¯⁵ mm

500 mm

2 x 10¯³ mm

5 x 10¯³ mm

53. Curtain less windows are made by making use of __________ of light.

Absorption

Polarization

Diffraction

Transmission

54. In the Michelson Interferometer, if m number fringes pass through a reference point when the mirror is moved a distance d, then the wavelength of the light can be found by the formula:

λ = 2d/m

λ = dm

λ = 2π dm

2λ = dm

55. A ____________ lens is used to form Newton’s rings.

Plano-concave

Plano-convex

Convexo-concave

Double-convex

56. Light appears to travel in straight lies since

Its velocity is very large

Its wavelength is very small

It is not absorbed by the atmosphere

It is reflected by the atmosphere

57. Which effect provides direct experimental evidence that light is a transverse, rather than a longitudinal, wave motion?

Light can be diffracted

Two coherent light waves can be made to interfere

The intensity of light from a point source falls off inversely as the square of the distance from the source

Light can be polarized

58. Two sources of light are coherent if they emit rays of

Same amplitude and wavelength

Same wavelength

Same wave length with constant phase difference

Same amplitude of vibration

59. Coherent monochromatic light illuminates two narrow parallel slits and the interference pattern that results is observed on a screen some distance beyond the slits. Which modification increases the separation between the dark lines of the interference pattern?

Using monochromatic light of longer wavelength

Using monochromatic light of higher frequency

Decreasing the distance between the screen and the slits

Increasing the distance between the slits

60. In an interference pattern

Bright fringes are wider than dark fringes

Central fringes are brighter than the outer fringes

Dark fringes are wider than bright fringe

Both dark and bright fringes are of equal width

61. Longitudinal waves do not exhibit

Reflection

Polarization

Refraction

Diffraction

62. Huygen’s wave theory of light cannot explain

Diffraction

Interference

Polarization

Photoelectric effect

63. A spherical wave front is that which has

A point source

None of these

A extended source

A source

64. Crystals of a material can behave as

Diffraction grating

Interferometer

Concave

Convex lens

65. Ultra – violet rays differ from X-rays in that ultra – violet rays

Cannot be diffracted

Cannot be polarized

Do not affect a photographic plate

Have a lower frequency

66. The fringe spacing in case of blue light

None of these

Increases

Decrease

Remains the same

67. Huygen’s wave theory of light cannot explain

Photoelectric effect

Diffraction

Polarization

Interference

68. On a rainy day, if there is an oil drop on tar road, colored rings are seen around this drop. This is because of

Diffraction pattern

Polarization

Interference pattern produced due to thin oil film

Total internal reflection of light

69. One condition for interference is that the two sources should be coherent and:

At a far off distance

Opposite to each other

Close together

Coinciding

70. Appearance of colour in thin films is due to

Dispersion

Diffraction

Interference

Polarization

71. Polarization occurs only in ________ waves

Mechanical waves

Matter waves

Transverse

Longitudinal

72. For the sustained interference of light, the necessary condition is that the two sources should

Have constant phase difference

Of same amplitude

Be narrow

Be close to each other

73. Which one of the following cannot be polarized?

Ultraviolet rays

Radio waves

X-rays

Sound waves

74. According to the electromagnetic theory, the speed of light is approximately:

3 x 10⁵ ms¯¹

3 x 10⁸ ms¯¹

3.1 x 10⁸ ms¯¹

3 x 10¯¹⁰ ms¯¹

75. Can two head lights of car can produce interference

Yes

None of these

Partly produce interference

Page 4 of 4

76. Intensities of the two waves of light are l and 4l. The maximum intensity of the resultant wave after superposition is

16l

25l

77. Signal from a remote control to the device operated by it tracels with the speed of:

Supersonics

Ultrasonics

Sound

Light

78. The principle of Michelson’s interferometers is

Refraction

Dispersion

Interference

Reflection

79. The setting of Newton’s rings is

A Plano convex lens and the plane glass plate

A Plano convex lens (long focal length) and the plane of glass plate

None of these

A Plano convex lens and simple glass sheet

80. Which one of the following phenomena is not explained by Huygen’s construction of wave front?

Diffraction

Refraction

Origin of spectra

Reflection

81. Which of the following has least wavelength?

Ultra-violet rays

X-rays

Cosmic-rays

γ-rays

82. Diffraction fringes are

They are adjacent with no space in between

Distance between then decreases

Distance between them increases

Equally spaced

83. In Newton’s rings the point of contact of the lend and the glass plate, the air film is

None of these

Zero

Minimum

Maximum

84. An oil surface floating on water surface exhibits beautiful colour patter, which is due to

Reflection of light

Diffraction of light

None of these

Interference of light

85. If the path difference must be half-integral number wavelength

d sin θ = (m + 1/2)π/λ

d sin θ = (m + 1)λ

d in θ = (m + ½ )1/λ

d sin θ = (m + 1/2)λ

86. The blue colour of the sky is due to

Reflection

Diffraction

Polarization

Scattering

87. Due to Plano convex lens and the plane glass plate the thickness of air film changes from the center to outward

It is constant at the center

Decreasing gradually

None of these

Increasing gradually

88. Wavelength of light of frequency 100 Hz is

2 x 10⁶ m

3 x 10⁶ m

5 x 10⁶ m

4 x 10⁶ m

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Maan AliLast Updated: April 18, 2025

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5 Comments

Trendsetter says:

September 5, 2021 at 2:27 pm

Idea of light as a wave was proposed by Huygen not young.

The best says:

June 30, 2020 at 5:40 pm

Light is a type of energy which produces sensation of vision.

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August 24, 2017 at 5:13 pm

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April 26, 2017 at 11:07 am

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umair ahmed says:

March 21, 2017 at 1:26 am

if some is one is using this website so plz reply

ECAT Physics Lights and Optics Online Test

Physics Lights and Optics MCQS Online Test

ECAT Physics Lights and Optics Chapter Online Test

Physics Lights and Optics Chapter Online Test

Physics

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Physics Lights and Optics MCQS Online Test

ECAT Physics Lights and Optics Chapter Online Test

Physics Lights and Optics Chapter Online Test

Physics

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