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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.
Test Helpful For:	ECAT Entry Test Physics Online Test Interview Questions about Physics All Universities Entrance Test Recruitments Tests

Physics Lights and Optics Chapter Online Test

Page 1 of 4

Physics

1. Polarization occurs only in ________ waves

Longitudinal

Mechanical waves

Matter waves

Transverse

2. Huygen’s wave theory of light cannot explain

Photoelectric effect

Interference

Polarization

Diffraction

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

Source

Base

Producer

Origin

4. In a plane polarized light

Vibration in all direction

Vibration in two mutually perpendicular directions

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

No vibration at all

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

Speed of propagation less than the wave

Speed of propagation of the wave

Speed of propagation greater than wave

B and C

6. In an interference pattern

Bright fringes are wider than dark fringes

Both dark and bright fringes are of equal width

Central fringes are brighter than the outer fringes

Dark fringes are wider than bright fringe

7. 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 10¹¹ to 5 x 10¹⁴ Hz

5 x 10⁵ to 5 x 10¹¹ Hz

8. 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

Increasing gradually

Decreasing gradually

None of these

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

A ray

Wave front

A half-period zone

Vibrator

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

Cannot be diffracted

Do not affect a photographic plate

Have a lower frequency

Cannot be polarized

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

Of same frequency

Of the same frequency and having definite phase relationship

Of nearly the same frequency

Different wavelength

12. 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

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

At a far off distance

Coinciding

Opposite to each other

Close together

14. Ray optics is valid, when characteristic dimensions are

Much larger than the wavelength of light

Of the same order as the wavelength of light

Much smaller than the wavelength of length

Of the order of one millimeter

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

Interference of light

None of these

Reflection of light

Diffraction of light

16. 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 = dm

λ = 2d/m

λ = 2π dm

2λ = dm

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

Bragg’s law

Huygen’s formula

Laue’s pattern

Compton effect

18. The fringe spacing in case of blue light

Decrease

Remains the same

None of these

Increases

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

Frequency

All of these

Phase

Wavelength

20. 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

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

Polarization

Transmission

Diffraction

Absorption

22. The blue colour of the sky is due to

Reflection

Diffraction

Scattering

Polarization

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

Distance between the slits

Fringe width

Wavelength

Intensity ratio of the sources

24. 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

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

Be narrow

Have constant phase difference

Of same amplitude

Be close to each other

Page 2 of 4

26. Choose the correct statement

Rays are normal to wave front

Rays may be normal to wave front

Rays are not normal to wave front

There is no relationship between rays and wave fronts

27. For constructive interference the path difference is

½ mλ

(m – 1)λ

Mλ

m²λ

28. Appearance of colour in thin films is due to

Polarization

Interference

Dispersion

Diffraction

29. The idea of light as wave produced by

Newton

Huygen

Thomos young

Michelson

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

Not comparable

Comparable

Both

None of these

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

Same wave length with constant phase difference

Same wavelength

Same amplitude and wavelength

Same amplitude of vibration

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

None of these

Interference

Doppler’s effect

Diffraction

33. 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

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

Ultrasonics

Supersonics

Sound

Light

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

3 x 10¯¹⁰ ms¯¹

3 x 10⁵ ms¯¹

3 x 10⁸ ms¯¹

3.1 x 10⁸ ms¯¹

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

Constructive interference

Destructive interference

Polarization

Diffraction

37. Longitudinal waves do not exhibit

Diffraction

Refraction

Reflection

Polarization

38. 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

39. Diffraction fringes are

Equally spaced

They are adjacent with no space in between

Distance between them increases

Distance between then decreases

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

A longitudinal wave

A transverse waves

An electromagnetic wave

A sound wave

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

m Sin θ = (d + 1/2)λ

d Sin θ = (m + 1/2)λ

2π Sin θ = (m + 1/2)λ

½ d Sin θ = mλ

42. 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

5 x 10¯³ mm

2 x 10¯³ mm

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

Both reflected and refracted light

Neither reflected nor refracted light

Reflected light

Refracted light

44. 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

45. Which of the following has least wavelength?

X-rays

γ-rays

Ultra-violet rays

Cosmic-rays

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

Elliptical

Parabolic

Circular

Straight

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

?/6

?/4

?/3

?/2

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

Diffraction

Origin of spectra

Refraction

Reflection

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

Wavelength

Wave front

Wave number

Wave form

50. Light on passing through a Polaroid is

Un-polarized

Circularly polarized

Plane polarized

Elliptically polarized

Page 3 of 4

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

Incoherent

In the form of a narrow beam

Electromagnetic

Monochromatic

52. The setting of Newton’s rings is

A Plano convex lens and simple glass sheet

None of these

A Plano convex lens and the plane glass plate

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

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

Emission spectrum

All of these

Line spectrum

Continuous emission spectrum

54. The cause of mirage observed in desert is

Refraction

Reflection

Total internal reflection

Scattering

55. A polarizer is used to

Increase intensity of light

Produce unpolarised light

Produce polarized light

Reduced intensity of light

56. Diffraction effect is

Less for a round edge

Less for a sharp edge

More for a round edge

More for a sharp edge

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

None of these

Newton

Huygen

Young

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

Reflection

Interference

Diffraction

Polarization

59. 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 high velocity waves

Laser rays are not absorbed

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

Crest

Trough

Wave front

Wavelength

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

d sin θ = (m + 1/2)π/λ

d sin θ = (m + 1/2)λ

d in θ = (m + ½ )1/λ

d sin θ = (m + 1)λ

62. Central spot of New tons rings

Dart for large wavelength

Dark

Bright

Bright for large wavelength

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

Source of wave front

Source

Source of secondary wave front

None of these

64. Wavelength of light of frequency 100 Hz is

4 x 10⁶ m

2 x 10⁶ m

3 x 10⁶ m

5 x 10⁶ m

65. 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

Diffraction pattern

Polarization

Total internal reflection of light

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

d sin θ = m/2 λ

md cos θ = λ

d sin θ = mλ

d sin θ = 2λm

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

Vision

Feeling

None of these

Sound

68. The principle of Michelson’s interferometers is

Dispersion

Interference

Refraction

Reflection

69. Light appears to travel in straight lies since

It is reflected by the atmosphere

Its velocity is very large

It is not absorbed by the atmosphere

Its wavelength is very small

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

Transmission

Refraction

Reflection

Diffraction

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

Interference with bright bands

Interference with dark bands

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

Zero

Maximum

Minimum

None of these

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

16l

25l

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

Reflection

Refraction

Diffraction

Interference

75. Crystals of a material can behave as

Convex lens

Concave

Interferometer

Diffraction grating

Page 4 of 4

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

Refraction

Reflection

Origin of spectra

Diffraction

77. Can two head lights of car can produce interference

Yes

None of these

Partly produce interference

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

Intensity

Energy

Momentum

Amplitude

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

Impossible to predict

Alternate dark and bright fringes will be seen

No interference fringes will be seen

Colored fringes will be seen

80. Which one of the following cannot be polarized?

Ultraviolet rays

Sound waves

Radio waves

X-rays

81. Huygen’s wave theory of light cannot explain

Polarization

Photoelectric effect

Interference

Diffraction

82. 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

Total internal reflection of light

Interference pattern produced due to thin oil film

Polarization

83. A spherical wave front is that which has

A extended source

None of these

A source

A point source

84. 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

Increasing the distance between the slits

Decreasing the distance between the screen and the slits

Using monochromatic light of higher frequency

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

Convexo-concave

Plano-concave

Double-convex

Plano-convex

86. 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

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

In the form of a narrow beam

Electromagnetic

Incoherent

Monochromatic

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

Two coherent light waves can be made to interfere

Light can be diffracted

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

Light can be polarized

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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

Physics

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