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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 appears to travel in straight lies since

It is not absorbed by the atmosphere

Its wavelength is very small

It is reflected by the atmosphere

Its velocity is very large

2. The fringe spacing in case of blue light

Increases

Decrease

Remains the same

None of these

3. 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

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

3 x 10¯¹⁰ ms¯¹

3 x 10⁸ ms¯¹

3.1 x 10⁸ ms¯¹

3 x 10⁵ ms¯¹

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

16l

25l

6. 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

7. Wavelength of light of frequency 100 Hz is

3 x 10⁶ m

5 x 10⁶ m

2 x 10⁶ m

4 x 10⁶ m

8. Which of the following has least wavelength?

Ultra-violet rays

γ-rays

X-rays

Cosmic-rays

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

Frequency

All of these

Wavelength

Phase

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

Have a lower frequency

Cannot be polarized

Do not affect a photographic plate

Cannot be diffracted

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

Refracted light

Reflected light

Neither reflected nor refracted light

Both reflected and refracted light

12. Polarization occurs only in ________ waves

Transverse

Matter waves

Mechanical waves

Longitudinal

13. 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

Interference pattern produced due to thin oil film

Total internal reflection of light

Diffraction pattern

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

Line spectrum

Continuous emission spectrum

Emission spectrum

All of these

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

A cylindrical wave front

An elliptical wave front

A plane wave front

A spherical wave front

16. 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

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

Wavelength

Wave front

Wave form

Wave number

18. 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 higher frequency

Increasing the distance between the slits

Using monochromatic light of longer wavelength

Decreasing the distance between the screen and the slits

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

Constructive interference

Diffraction

Polarization

Destructive interference

20. The idea of light as wave produced by

Michelson

Thomos young

Huygen

Newton

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

Not comparable

Comparable

Both

None of these

22. The principle of Michelson’s interferometers is

Reflection

Refraction

Dispersion

Interference

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

Reflection

Origin of spectra

Refraction

Diffraction

24. In an interference pattern

Central fringes are brighter than the outer fringes

Dark fringes are wider than bright fringe

Bright fringes are wider than dark fringes

Both dark and bright fringes are of equal width

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

Feeling

Sound

Vision

None of these

Page 2 of 4

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

Electromagnetic

Monochromatic

In the form of a narrow beam

Incoherent

27. Ray optics is valid, when characteristic dimensions are

Of the same order as the wavelength of light

Much smaller than the wavelength of length

Of the order of one millimeter

Much larger than the wavelength of light

28. Light on passing through a Polaroid is

Un-polarized

Circularly polarized

Plane polarized

Elliptically polarized

29. Huygen’s wave theory of light cannot explain

Interference

Polarization

Diffraction

Photoelectric effect

30. Which one of the following cannot be polarized?

Ultraviolet rays

Sound waves

X-rays

Radio waves

31. Huygen’s wave theory of light cannot explain

Interference

Photoelectric effect

Polarization

Diffraction

32. Appearance of colour in thin films is due to

Polarization

Interference

Dispersion

Diffraction

33. 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 diffracted

Two coherent light waves can be made to interfere

Light can be polarized

34. The setting of Newton’s rings is

None of these

A Plano convex lens and simple glass sheet

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

A Plano convex lens and the plane glass plate

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

Momentum

Intensity

Energy

Amplitude

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

Laser rays propagate in a straight line

Laser rays are high velocity waves

Laser rays are not absorbed

Laser rays are most coherent waves

37. 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

None of these

Decreasing gradually

Increasing gradually

38. 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

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

Colored fringes will be seen

Impossible to predict

No interference fringes will be seen

Alternate dark and bright fringes will be seen

40. Central spot of New tons rings

Bright for large wavelength

Bright

Dart for large wavelength

Dark

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

2 x 10¯⁵ mm

5 x 10¯³ mm

2 x 10¯³ mm

500 mm

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

Source

Origin

Base

Producer

43. Crystals of a material can behave as

Concave

Interferometer

Convex lens

Diffraction grating

44. 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

45. A polarizer is used to

Produce polarized light

Produce unpolarised light

Increase intensity of light

Reduced intensity of light

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

Ultrasonics

Supersonics

Light

Sound

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

Straight

Parabolic

Circular

Elliptical

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

Distance between the slits

Wavelength

Fringe width

Intensity ratio of the sources

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

Polarization

Absorption

Transmission

Diffraction

50. 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 dark bands

Interference with bright bands

Interference in which breadth of the fringe will be slightly increase

No interference

Page 3 of 4

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

Diffraction

Transmission

Reflection

Refraction

52. The cause of mirage observed in desert is

Scattering

Reflection

Total internal reflection

Refraction

53. A spherical wave front is that which has

A extended source

None of these

A source

A point source

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

Refraction

Interference

Diffraction

Reflection

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

Source of secondary wave front

None of these

Source

Source of wave front

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

d sin θ = mλ

d sin θ = 2λm

md cos θ = λ

d sin θ = m/2 λ

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

A transverse waves

A sound wave

An electromagnetic wave

A longitudinal wave

58. Can two head lights of car can produce interference

None of these

Partly produce interference

Yes

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

Energy of different colors is different

Velocity of different colors is different

Amplitude of different colors is different

Phase of different colors is different

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

?/3

?/2

?/4

?/6

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

B and C

Speed of propagation less than the wave

Speed of propagation greater than wave

Speed of propagation of the wave

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

Coinciding

At a far off distance

Close together

Opposite to each other

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

Y = (m + 1) λL/d

Y = (m + 1/2) λd/L

Y = (m + 1/2) λL/d

Y = (m + ½) dL/λ

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

½ d Sin θ = mλ

d Sin θ = (m + 1/2)λ

m Sin θ = (d + 1/2)λ

2π Sin θ = (m + 1/2)λ

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

Diffraction of light

Interference of light

None of these

Reflection of light

66. Choose the correct statement

Rays may be normal to wave front

Rays are not normal to wave front

There is no relationship between rays and wave fronts

Rays are normal to wave front

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

d sin θ = (m + 1)λ

d in θ = (m + ½ )1/λ

d sin θ = (m + 1/2)λ

d sin θ = (m + 1/2)π/λ

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

Same amplitude of vibration

Same wavelength

Same wave length with constant phase difference

Same amplitude and wavelength

69. Diffraction fringes are

Equally spaced

They are adjacent with no space in between

Distance between them increases

Distance between then decreases

70. In a plane polarized light

Vibration in two mutually perpendicular directions

No vibration at all

Vibration in all direction

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

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

None of these

Different width

Equal width

Dark fringes are thicker than bright

72. 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 10⁵ to 5 x 10⁵ Hz

5 x 10¹¹ to 5 x 10¹⁴ Hz

5 x 10¹⁴ to 5 x 10¹⁷ Hz

5 x 10⁵ to 5 x 10¹¹ Hz

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

Convexo-concave

Double-convex

Plano-concave

Plano-convex

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

Wave front

Trough

Crest

Wavelength

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

Line absorption spectrum

Line emission spectrum

Band emission spectrum

Band absorption spectrum

Page 4 of 4

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

Monochromatic

Electromagnetic

Incoherent

In the form of a narrow beam

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

Light can be diffracted

Light can be polarized

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

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

Laue’s pattern

Compton effect

Bragg’s law

Huygen’s formula

79. 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

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

Young

Newton

None of these

Huygen

81. For constructive interference the path difference is

m²λ

(m – 1)λ

Mλ

½ mλ

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

Diffraction

Polarization

Reflection

Interference

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

Reflection

Diffraction

Origin of spectra

Refraction

84. The blue colour of the sky is due to

Reflection

Polarization

Scattering

Diffraction

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

Be narrow

Of same amplitude

Have constant phase difference

Be close to each other

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

Integral multiple of λ/2

Integral multiple of λ

Odd integral multiple of λ/2

Even integral multiple of λ

87. Diffraction effect is

More for a round edge

More for a sharp edge

Less for a round edge

Less for a sharp edge

88. Longitudinal waves do not exhibit

Refraction

Reflection

Polarization

Diffraction

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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

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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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