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

Vibrator

A ray

Wave front

A half-period zone

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

Alternate dark and bright fringes will be seen

No interference fringes will be seen

Colored fringes will be seen

Impossible to predict

3. The principle of Michelson’s interferometers is

Dispersion

Reflection

Interference

Refraction

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

Bragg’s law

Huygen’s formula

Laue’s pattern

Compton effect

5. 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?

Increasing the distance between the slits

Decreasing the distance between the screen and the slits

Using monochromatic light of longer wavelength

Using monochromatic light of higher frequency

6. Longitudinal waves do not exhibit

Reflection

Refraction

Diffraction

Polarization

7. 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 in which breadth of the fringe will be slightly increase

Interference with bright bands

No interference

Interference with dark bands

8. Choose the correct statement

There is no relationship between rays and wave fronts

Rays may be normal to wave front

Rays are not normal to wave front

Rays are normal to wave front

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

Coinciding

Close together

At a far off distance

Opposite to each other

10. 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

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

d sin θ = (m + 1)λ

d sin θ = (m + 1/2)π/λ

d in θ = (m + ½ )1/λ

d sin θ = (m + 1/2)λ

12. The blue colour of the sky is due to

Polarization

Diffraction

Scattering

Reflection

13. 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 10¹⁴ to 5 x 10¹⁷ Hz

5 x 10⁵ to 5 x 10¹¹ Hz

5 x 10⁵ to 5 x 10⁵ Hz

5 x 10¹¹ to 5 x 10¹⁴ Hz

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

?/2

?/4

?/3

?/6

15. In a plane polarized light

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

Vibration in two mutually perpendicular directions

Vibration in all direction

No vibration at all

16. Appearance of colour in thin films is due to

Interference

Diffraction

Polarization

Dispersion

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

Reflection

Refraction

Interference

Diffraction

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

Source of secondary wave front

Source

Source of wave front

None of these

19. 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

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

Constructive interference

Polarization

Destructive interference

Diffraction

21. 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

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

Equal width

Different width

Dark fringes are thicker than bright

None of these

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

Be narrow

Be close to each other

Of same amplitude

Have constant phase difference

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

None of these

Diffraction

Doppler’s effect

Interference

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

A plane wave front

A spherical wave front

An elliptical wave front

A cylindrical wave front

Page 2 of 4

26. Diffraction fringes are

Distance between then decreases

Equally spaced

They are adjacent with no space in between

Distance between them increases

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

Wavelength

Wave front

Trough

Crest

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

500 mm

2 x 10¯³ mm

5 x 10¯³ mm

2 x 10¯⁵ mm

29. Which one of the following cannot be polarized?

Radio waves

X-rays

Ultraviolet rays

Sound waves

30. Ray optics is valid, when characteristic dimensions are

Much smaller than the wavelength of length

Of the order of one millimeter

Much larger than the wavelength of light

Of the same order as the wavelength of light

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

Speed of propagation greater than wave

Speed of propagation less than the wave

B and C

Speed of propagation of the wave

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

Ultrasonics

Light

Sound

Supersonics

33. Diffraction effect is

More for a round edge

More for a sharp edge

Less for a round edge

Less for a sharp edge

34. A spherical wave front is that which has

A source

A point source

A extended source

None of these

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

Newton

Huygen

Young

None of these

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

Wavelength

Frequency

Phase

All of these

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

Diffraction

Interference

Reflection

Polarization

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

Feeling

None of these

Sound

Vision

39. The fringe spacing in case of blue light

Remains the same

Decrease

Increases

None of these

40. Crystals of a material can behave as

Concave

Diffraction grating

Interferometer

Convex lens

41. 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

42. The idea of light as wave produced by

Thomos young

Huygen

Michelson

Newton

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

Do not affect a photographic plate

Cannot be polarized

Cannot be diffracted

Have a lower frequency

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

A longitudinal wave

A transverse waves

An electromagnetic wave

A sound wave

45. For constructive interference the path difference is

½ mλ

(m – 1)λ

m²λ

Mλ

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

16l

25l

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

½ d Sin θ = mλ

m Sin θ = (d + 1/2)λ

2π Sin θ = (m + 1/2)λ

d Sin θ = (m + 1/2)λ

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

Not comparable

Both

None of these

Comparable

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

Total internal reflection of light

Polarization

Interference pattern produced due to thin oil film

Diffraction pattern

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

Integral multiple of λ

Even integral multiple of λ

Odd integral multiple of λ/2

Integral multiple of λ/2

Page 3 of 4

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

In the form of a narrow beam

Electromagnetic

Incoherent

Monochromatic

52. Wavelength of light of frequency 100 Hz is

3 x 10⁶ m

5 x 10⁶ m

2 x 10⁶ m

4 x 10⁶ m

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

Same wavelength

Same wave length with constant phase difference

Same amplitude of vibration

Same amplitude and wavelength

54. In an interference pattern

Central fringes are brighter than the outer fringes

Both dark and bright fringes are of equal width

Dark fringes are wider than bright fringe

Bright fringes are wider than dark fringes

55. A polarizer is used to

Produce polarized light

Reduced intensity of light

Increase intensity of light

Produce unpolarised light

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

Double-convex

Plano-concave

Convexo-concave

Plano-convex

57. 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 = 2π dm

2λ = dm

λ = 2d/m

λ = dm

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

Refraction

Diffraction

Origin of spectra

Reflection

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

Transmission

Reflection

Diffraction

Refraction

60. 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

Light can be diffracted

Two coherent light waves can be made to interfere

61. The cause of mirage observed in desert is

Scattering

Refraction

Reflection

Total internal reflection

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

None of these

It is constant at the center

Increasing gradually

Decreasing gradually

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

Wave form

Wavelength

Wave front

Wave number

64. Huygen’s wave theory of light cannot explain

Photoelectric effect

Diffraction

Polarization

Interference

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

Absorption

Polarization

Diffraction

Transmission

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

3 x 10⁵ ms¯¹

3.1 x 10⁸ ms¯¹

3 x 10¯¹⁰ ms¯¹

3 x 10⁸ ms¯¹

67. Light appears to travel in straight lies since

It is reflected by the atmosphere

Its velocity is very large

Its wavelength is very small

It is not absorbed by the atmosphere

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

Interference pattern produced due to thin oil film

Polarization

Total internal reflection of light

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

Electromagnetic

Monochromatic

Incoherent

In the form of a narrow beam

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

All of these

Line spectrum

Emission spectrum

Continuous emission spectrum

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

Laser rays are most coherent waves

Laser rays propagate in a straight line

Laser rays are not absorbed

Laser rays are high velocity waves

72. Polarization occurs only in ________ waves

Longitudinal

Transverse

Mechanical waves

Matter waves

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

Different wavelength

Of same frequency

Of the same frequency and having definite phase relationship

Of nearly the same frequency

74. Can two head lights of car can produce interference

None of these

Yes

Partly produce interference

75. Huygen’s wave theory of light cannot explain

Polarization

Interference

Diffraction

Photoelectric effect

Page 4 of 4

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

Reflection

Origin of spectra

Refraction

Diffraction

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

Y = (m + 1) λL/d

Y = (m + ½) dL/λ

Y = (m + 1/2) λd/L

Y = (m + 1/2) λL/d

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

None of these

Minimum

Maximum

Zero

79. The setting of Newton’s rings is

A Plano convex lens and the plane glass plate

A Plano convex lens and simple glass sheet

None of these

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

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

Fringe width

Wavelength

Distance between the slits

Intensity ratio of the sources

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

Amplitude

Intensity

Momentum

Energy

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

d sin θ = mλ

d sin θ = 2λm

d sin θ = m/2 λ

md cos θ = λ

83. Light on passing through a Polaroid is

Elliptically polarized

Plane polarized

Un-polarized

Circularly polarized

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

Reflection of light

Interference of light

None of these

Diffraction of light

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

Producer

Source

Base

Origin

86. Which of the following has least wavelength?

X-rays

γ-rays

Ultra-violet rays

Cosmic-rays

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

Amplitude of different colors is different

Phase of different colors is different

Velocity of different colors is different

Energy of different colors is different

88. Central spot of New tons rings

Dark

Bright for large wavelength

Bright

Dart for large wavelength

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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.

Chaudry Adnan says:

August 24, 2017 at 5:13 pm

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April 26, 2017 at 11:07 am

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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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