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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. Light on passing through a Polaroid is

Elliptically polarized

Circularly polarized

Plane polarized

Un-polarized

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

Odd integral multiple of λ/2

Integral multiple of λ/2

Integral multiple of λ

Even integral multiple of λ

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

Momentum

Amplitude

Energy

Intensity

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

Ultrasonics

Supersonics

Sound

Light

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

Phase of different colors is different

Velocity of different colors is different

Energy of different colors is different

Amplitude of different colors is different

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

None of these

Reflection of light

Interference of light

Diffraction of light

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

Of nearly the same frequency

Different wavelength

Of same frequency

Of the same frequency and having definite phase relationship

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

B and C

Speed of propagation of the wave

Speed of propagation greater than wave

Speed of propagation less than the wave

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

Polarization

Total internal reflection of light

Interference pattern produced due to thin oil film

Diffraction pattern

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

Newton

Huygen

Young

None of these

11. The fringe spacing in case of blue light

Remains the same

Increases

Decrease

None of these

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

Origin

Base

Producer

Source

13. A polarizer is used to

Increase intensity of light

Produce polarized light

Reduced intensity of light

Produce unpolarised light

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

?/4

?/2

?/3

?/6

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

5 x 10¯³ mm

500 mm

2 x 10¯³ mm

2 x 10¯⁵ mm

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

Polarization

Diffraction

Absorption

Transmission

17. For constructive interference the path difference is

½ mλ

m²λ

(m – 1)λ

Mλ

18. 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

Diffraction pattern

Polarization

Interference pattern produced due to thin oil film

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

An electromagnetic wave

A longitudinal wave

A transverse waves

A sound wave

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

Incoherent

In the form of a narrow beam

Monochromatic

Electromagnetic

21. Light appears to travel in straight lies since

It is reflected by the atmosphere

It is not absorbed by the atmosphere

Its wavelength is very small

Its velocity is very large

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

Line absorption spectrum

Band absorption spectrum

Line emission spectrum

Band emission spectrum

23. In an interference pattern

Dark fringes are wider than bright fringe

Both dark and bright fringes are of equal width

Central fringes are brighter than the outer fringes

Bright fringes are wider than dark fringes

24. Appearance of colour in thin films is due to

Polarization

Interference

Diffraction

Dispersion

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

3 x 10⁵ ms¯¹

3 x 10⁸ ms¯¹

3 x 10¯¹⁰ ms¯¹

3.1 x 10⁸ ms¯¹

Page 2 of 4

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

Increasing gradually

None of these

It is constant at the center

Decreasing gradually

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

At a far off distance

Opposite to each other

Coinciding

Close together

28. Wavelength of light of frequency 100 Hz is

2 x 10⁶ m

4 x 10⁶ m

5 x 10⁶ m

3 x 10⁶ m

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

All of these

Phase

Frequency

Wavelength

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

Wave number

Wavelength

Wave front

Wave form

31. The cause of mirage observed in desert is

Reflection

Refraction

Total internal reflection

Scattering

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

Distance between the slits

Wavelength

Intensity ratio of the sources

Fringe width

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

Laue’s pattern

Huygen’s formula

Bragg’s law

Compton effect

34. Which of the following has least wavelength?

X-rays

γ-rays

Ultra-violet rays

Cosmic-rays

35. The principle of Michelson’s interferometers is

Reflection

Refraction

Dispersion

Interference

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

d sin θ = (m + 1/2)λ

d sin θ = (m + 1/2)π/λ

d sin θ = (m + 1)λ

d in θ = (m + ½ )1/λ

37. The idea of light as wave produced by

Newton

Michelson

Huygen

Thomos young

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

None of these

Sound

Vision

Feeling

39. 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

No interference

Interference with dark bands

Interference with bright bands

Interference in which breadth of the fringe will be slightly increase

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

Continuous emission spectrum

Emission spectrum

Line spectrum

All of these

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

Wave front

Wavelength

Crest

Trough

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

Interference

Reflection

Diffraction

Polarization

43. Crystals of a material can behave as

Concave

Convex lens

Diffraction grating

Interferometer

44. Huygen’s wave theory of light cannot explain

Interference

Diffraction

Photoelectric effect

Polarization

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

Monochromatic

In the form of a narrow beam

Electromagnetic

Incoherent

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

d sin θ = m/2 λ

d sin θ = 2λm

d sin θ = mλ

md cos θ = λ

47. The setting of Newton’s rings is

A Plano convex lens and the plane glass plate

A Plano convex lens and simple glass sheet

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

None of these

48. The blue colour of the sky is due to

Reflection

Scattering

Polarization

Diffraction

49. 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?

Decreasing the distance between the screen and the slits

Using monochromatic light of longer wavelength

Using monochromatic light of higher frequency

Increasing the distance between the slits

50. 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

Page 3 of 4

51. A spherical wave front is that which has

A point source

A source

A extended source

None of these

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

No interference fringes will be seen

Colored fringes will be seen

Impossible to predict

Alternate dark and bright fringes will be seen

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

Comparable

Not comparable

None of these

Both

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

Circular

Elliptical

Parabolic

Straight

55. Central spot of New tons rings

Bright for large wavelength

Dark

Dart for large wavelength

Bright

56. 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

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

Wave front

A half-period zone

Vibrator

A ray

58. Longitudinal waves do not exhibit

Reflection

Polarization

Refraction

Diffraction

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

Reflection

Refraction

Diffraction

Interference

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

Convexo-concave

Plano-convex

Plano-concave

Double-convex

61. Which one of the following cannot be polarized?

Sound waves

Ultraviolet rays

Radio waves

X-rays

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

Maximum

Minimum

None of these

Zero

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

Diffraction

Refraction

Transmission

Reflection

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

Y = (m + 1/2) λL/d

Y = (m + ½) dL/λ

Y = (m + 1) λL/d

Y = (m + 1/2) λd/L

65. 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

66. 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 10⁵ Hz

5 x 10⁵ to 5 x 10¹¹ Hz

5 x 10¹¹ to 5 x 10¹⁴ Hz

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

Diffraction

Polarization

Destructive interference

Constructive interference

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

Both reflected and refracted light

Reflected light

Refracted light

Neither reflected nor refracted light

69. Polarization occurs only in ________ waves

Longitudinal

Transverse

Matter waves

Mechanical waves

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

Diffraction

Refraction

Reflection

Origin of spectra

71. In a plane polarized light

Vibration in two mutually perpendicular directions

Vibration in all direction

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

No vibration at all

72. Huygen’s wave theory of light cannot explain

Photoelectric effect

Interference

Polarization

Diffraction

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

25l

16l

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

Same amplitude of vibration

Same wave length with constant phase difference

Same amplitude and wavelength

Same wavelength

75. Ray optics is valid, when characteristic dimensions are

Much smaller than the wavelength of length

Of the order of one millimeter

Of the same order as the wavelength of light

Much larger than the wavelength of light

Page 4 of 4

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

Source of wave front

Source

Source of secondary wave front

None of these

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

Be narrow

Have constant phase difference

Be close to each other

Of same amplitude

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

Laser rays are high velocity waves

Laser rays are not absorbed

Laser rays are most coherent waves

Laser rays propagate in a straight line

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

Interference

Diffraction

Doppler’s effect

None of these

80. Diffraction effect is

Less for a sharp edge

More for a round edge

More for a sharp edge

Less for a round edge

81. Can two head lights of car can produce interference

None of these

Partly produce interference

Yes

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

A plane wave front

An elliptical wave front

A cylindrical wave front

A spherical wave front

83. Choose the correct statement

There is no relationship between rays and wave fronts

Rays may be normal to wave front

Rays are normal to wave front

Rays are not normal to wave front

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

2π Sin θ = (m + 1/2)λ

m Sin θ = (d + 1/2)λ

½ d Sin θ = mλ

d Sin θ = (m + 1/2)λ

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

Cannot be polarized

Do not affect a photographic plate

Have a lower frequency

Cannot be diffracted

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

Origin of spectra

Refraction

Diffraction

Reflection

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

Light can be diffracted

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

Two coherent light waves can be made to interfere

Light can be polarized

88. Diffraction fringes are

Equally spaced

Distance between then decreases

They are adjacent with no space in between

Distance between them increases

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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

agr is s tiyari krangay to hm uni test pas krlangy?

Abuzar says:

April 26, 2017 at 11:07 am

Agr koi Matric(9th+10th) and Fsc(11th+12th) and Ecat+Mcat k complete video lectures lena chahta h tou in nums pe contact kar

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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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Maan Ali

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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

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