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

Electromagnetic

Monochromatic

Incoherent

In the form of a narrow beam

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

Source of wave front

Source

None of these

Source of secondary wave front

3. The cause of mirage observed in desert is

Scattering

Reflection

Refraction

Total internal reflection

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

d in θ = (m + ½ )1/λ

d sin θ = (m + 1/2)λ

d sin θ = (m + 1)λ

d sin θ = (m + 1/2)π/λ

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

Sound

Vision

None of these

Feeling

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

Wavelength

Intensity ratio of the sources

Distance between the slits

Fringe width

7. 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:

2λ = dm

λ = dm

λ = 2π dm

λ = 2d/m

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

Dark fringes are thicker than bright

Equal width

Different width

None of these

9. The setting of Newton’s rings is

A Plano convex lens and simple glass sheet

None of these

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

A Plano convex lens and the plane glass plate

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

Young

Newton

None of these

Huygen

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

16l

25l

12. Diffraction fringes are

Distance between then decreases

Distance between them increases

They are adjacent with no space in between

Equally spaced

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

Transmission

Diffraction

Absorption

Polarization

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

None of these

Decreasing gradually

Increasing gradually

It is constant at the center

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

3 x 10¯¹⁰ ms¯¹

3 x 10⁸ ms¯¹

3 x 10⁵ ms¯¹

3.1 x 10⁸ ms¯¹

16. Choose the correct statement

Rays are normal to wave front

Rays may be normal to wave front

There is no relationship between rays and wave fronts

Rays are not normal to wave front

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

A cylindrical wave front

A spherical wave front

An elliptical wave front

A plane wave front

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

Not comparable

None of these

Both

Comparable

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

Line spectrum

Continuous emission spectrum

Emission spectrum

All of these

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

Of the same frequency and having definite phase relationship

Of same frequency

Different wavelength

Of nearly the same frequency

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

Polarization

Diffraction

Reflection

Interference

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

2 x 10¯³ mm

500 mm

5 x 10¯³ mm

2 x 10¯⁵ mm

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

Diffraction

None of these

Interference

Doppler’s effect

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

Wavelength

Wave front

Trough

Crest

25. 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

Page 2 of 4

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

Intensity

Energy

Amplitude

Momentum

27. In an interference pattern

Both dark and bright fringes are of equal width

Bright fringes are wider than dark fringes

Dark fringes are wider than bright fringe

Central fringes are brighter than the outer fringes

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

Wave front

A ray

Vibrator

A half-period zone

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

Base

Origin

Producer

Source

30. For constructive interference the path difference is

(m – 1)λ

½ mλ

m²λ

Mλ

31. Which one of the following cannot be polarized?

Radio waves

X-rays

Sound waves

Ultraviolet rays

32. Appearance of colour in thin films is due to

Dispersion

Diffraction

Polarization

Interference

33. 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

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

B and C

Speed of propagation greater than wave

Speed of propagation less than the wave

Speed of propagation of the wave

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

Diffraction

Polarization

Constructive interference

Destructive interference

36. Wavelength of light of frequency 100 Hz is

3 x 10⁶ m

5 x 10⁶ m

2 x 10⁶ m

4 x 10⁶ m

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

Diffraction

Refraction

Interference

Reflection

38. Longitudinal waves do not exhibit

Refraction

Reflection

Polarization

Diffraction

39. 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

40. 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

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

Bragg’s law

Laue’s pattern

Compton effect

Huygen’s formula

42. The fringe spacing in case of blue light

Decrease

Remains the same

Increases

None of these

43. Can two head lights of car can produce interference

None of these

Yes

Partly produce interference

44. 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 polarized

Light can be diffracted

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

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

All of these

Phase

Wavelength

Frequency

46. In a plane polarized light

Vibration in all direction

No vibration at all

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

Vibration in two mutually perpendicular directions

47. A spherical wave front is that which has

None of these

A point source

A extended source

A source

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

A longitudinal wave

A transverse waves

A sound wave

An electromagnetic wave

49. The principle of Michelson’s interferometers is

Refraction

Reflection

Dispersion

Interference

50. 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

Interference pattern produced due to thin oil film

Diffraction pattern

Polarization

Page 3 of 4

51. 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

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

Velocity of different colors is different

Amplitude of different colors is different

Phase of different colors is different

Energy of different colors is different

53. 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

Increasing the distance between the slits

Using monochromatic light of higher frequency

54. Ray optics is valid, when characteristic dimensions are

Of the order of one millimeter

Much larger than the wavelength of light

Of the same order as the wavelength of light

Much smaller than the wavelength of length

55. Polarization occurs only in ________ waves

Matter waves

Longitudinal

Transverse

Mechanical waves

56. 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

57. Which of the following has least wavelength?

Cosmic-rays

Ultra-violet rays

X-rays

γ-rays

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

Interference with bright bands

59. The idea of light as wave produced by

Huygen

Newton

Michelson

Thomos young

60. Crystals of a material can behave as

Diffraction grating

Concave

Convex lens

Interferometer

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

Diffraction

Origin of spectra

Refraction

Reflection

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

Neither reflected nor refracted light

Reflected light

Both reflected and refracted light

Refracted light

63. 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

64. Diffraction effect is

Less for a sharp edge

More for a round edge

Less for a round edge

More for a sharp edge

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

Supersonics

Sound

Light

Ultrasonics

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

Wavelength

Wave number

Wave form

Wave front

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

None of these

Diffraction of light

Reflection of light

Interference of light

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

Origin of spectra

Diffraction

Reflection

Refraction

69. The blue colour of the sky is due to

Diffraction

Reflection

Polarization

Scattering

70. 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

Even integral multiple of λ

Integral multiple of λ

71. A polarizer is used to

Reduced intensity of light

Produce polarized light

Produce unpolarised light

Increase intensity of light

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

?/4

?/3

?/2

?/6

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

Line emission spectrum

Line absorption spectrum

Band absorption spectrum

Band emission spectrum

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

Y = (m + 1/2) λL/d

Y = (m + 1) λL/d

Y = (m + 1/2) λd/L

Y = (m + ½) dL/λ

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

Maximum

None of these

Zero

Minimum

Page 4 of 4

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

No interference fringes will be seen

Impossible to predict

Alternate dark and bright fringes will be seen

Colored fringes will be seen

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

md cos θ = λ

d sin θ = mλ

d sin θ = 2λm

d sin θ = m/2 λ

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

Refraction

Transmission

Reflection

Diffraction

79. Light on passing through a Polaroid is

Un-polarized

Plane polarized

Elliptically polarized

Circularly polarized

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

Close together

Opposite to each other

At a far off distance

Coinciding

81. Central spot of New tons rings

Bright

Bright for large wavelength

Dart for large wavelength

Dark

82. Huygen’s wave theory of light cannot explain

Diffraction

Interference

Photoelectric effect

Polarization

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

Same amplitude of vibration

Same wave length with constant phase difference

Same wavelength

Same amplitude and wavelength

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

d Sin θ = (m + 1/2)λ

½ d Sin θ = mλ

2π Sin θ = (m + 1/2)λ

m Sin θ = (d + 1/2)λ

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

Double-convex

Plano-convex

Convexo-concave

Plano-concave

86. Huygen’s wave theory of light cannot explain

Diffraction

Photoelectric effect

Interference

Polarization

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

Elliptical

Straight

Circular

Parabolic

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

Electromagnetic

Monochromatic

In the form of a narrow beam

Incoherent

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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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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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