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

Crest

Wave front

Trough

Wavelength

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

Destructive interference

Constructive interference

Polarization

Diffraction

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

Young

None of these

Huygen

Newton

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

Coinciding

Close together

Opposite to each other

At a far off distance

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

Same wavelength

Same amplitude and wavelength

Same amplitude of vibration

Same wave length with constant phase difference

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

Integral multiple of λ

Odd integral multiple of λ/2

Even integral multiple of λ

Integral multiple of λ/2

7. Diffraction effect is

Less for a sharp edge

Less for a round edge

More for a sharp edge

More for a round edge

8. 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

Light can be polarized

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

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

Amplitude of different colors is different

Energy of different colors is different

Velocity of different colors is different

Phase of different colors is different

10. In an interference pattern

Central fringes are brighter than the outer fringes

Bright fringes are wider than dark fringes

Both dark and bright fringes are of equal width

Dark fringes are wider than bright fringe

11. Polarization occurs only in ________ waves

Mechanical waves

Matter waves

Longitudinal

Transverse

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

16l

25l

13. Light appears to travel in straight lies since

Its wavelength is very small

It is not absorbed by the atmosphere

It is reflected by the atmosphere

Its velocity is very large

14. 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) λL/d

Y = (m + 1/2) λd/L

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

Different wavelength

Of same frequency

Of nearly the same frequency

Of the same frequency and having definite phase relationship

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

None of these

Diffraction of light

Interference of light

Reflection of light

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

Intensity

Energy

Momentum

Amplitude

18. The cause of mirage observed in desert is

Reflection

Refraction

Total internal reflection

Scattering

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

Minimum

None of these

Zero

Maximum

20. 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

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

?/4

?/2

?/3

?/6

22. Central spot of New tons rings

Dark

Bright for large wavelength

Bright

Dart for large wavelength

23. 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 = 2π dm

λ = dm

λ = 2d/m

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

Straight

Circular

Parabolic

Elliptical

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

None of these

Not comparable

Both

Comparable

Page 2 of 4

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

Reflection

Diffraction

Interference

Refraction

27. 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

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

In the form of a narrow beam

Incoherent

Electromagnetic

Monochromatic

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

Laser rays are not absorbed

Laser rays are most coherent waves

Laser rays propagate in a straight line

Laser rays are high velocity waves

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

An elliptical wave front

A plane wave front

A spherical wave front

A cylindrical wave front

31. Light on passing through a Polaroid is

Circularly polarized

Un-polarized

Plane polarized

Elliptically polarized

32. 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

Diffraction pattern

Interference pattern produced due to thin oil film

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

Transmission

Absorption

Diffraction

Polarization

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

Different width

Equal width

Dark fringes are thicker than bright

None of these

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

None of these

Increasing gradually

It is constant at the center

Decreasing gradually

36. Appearance of colour in thin films is due to

Dispersion

Diffraction

Polarization

Interference

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

Feeling

None of these

Sound

Vision

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

Double-convex

Convexo-concave

Plano-concave

Plano-convex

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

All of these

Line spectrum

Continuous emission spectrum

Emission spectrum

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

Reflection

Refraction

Origin of spectra

Diffraction

42. The principle of Michelson’s interferometers is

Dispersion

Interference

Reflection

Refraction

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

d sin θ = (m + 1/2)π/λ

d in θ = (m + ½ )1/λ

d sin θ = (m + 1/2)λ

d sin θ = (m + 1)λ

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

Refraction

Diffraction

Reflection

Origin of spectra

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

3 x 10⁵ ms¯¹

3 x 10¯¹⁰ ms¯¹

3.1 x 10⁸ ms¯¹

3 x 10⁸ ms¯¹

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

Electromagnetic

In the form of a narrow beam

Monochromatic

Incoherent

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

Compton effect

Bragg’s law

Laue’s pattern

Huygen’s formula

48. Ray optics is valid, when characteristic dimensions are

Much larger than the wavelength of light

Much smaller than the wavelength of length

Of the order of one millimeter

Of the same order as the wavelength of light

49. A spherical wave front is that which has

A source

A point source

A extended source

None of these

50. Which of the following has least wavelength?

Ultra-violet rays

Cosmic-rays

X-rays

γ-rays

Page 3 of 4

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

Wave front

Wave number

Wavelength

Wave form

52. 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 dark bands

No interference

Interference with bright bands

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

A transverse waves

A longitudinal wave

An electromagnetic wave

A sound wave

54. Can two head lights of car can produce interference

None of these

Partly produce interference

Yes

55. Diffraction fringes are

Equally spaced

Distance between then decreases

They are adjacent with no space in between

Distance between them increases

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

Refracted light

Both reflected and refracted light

Neither reflected nor refracted light

Reflected light

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

Diffraction

Interference

Polarization

Reflection

58. 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

59. Which one of the following cannot be polarized?

X-rays

Sound waves

Radio waves

Ultraviolet rays

60. The blue colour of the sky is due to

Polarization

Scattering

Diffraction

Reflection

61. For constructive interference the path difference is

m²λ

½ mλ

(m – 1)λ

Mλ

62. Longitudinal waves do not exhibit

Polarization

Refraction

Diffraction

Reflection

63. The idea of light as wave produced by

Huygen

Thomos young

Michelson

Newton

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

Sound

Supersonics

Light

Ultrasonics

65. 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

Light can be polarized

Two coherent light waves can be made to interfere

66. The fringe spacing in case of blue light

None of these

Decrease

Increases

Remains the same

67. 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

68. Choose the correct statement

Rays may be normal to wave front

Rays are normal to wave front

Rays are not normal to wave front

There is no relationship between rays and wave fronts

69. Huygen’s wave theory of light cannot explain

Polarization

Interference

Photoelectric effect

Diffraction

70. Wavelength of light of frequency 100 Hz is

5 x 10⁶ m

3 x 10⁶ m

4 x 10⁶ m

2 x 10⁶ m

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

2 x 10¯⁵ mm

2 x 10¯³ mm

5 x 10¯³ mm

500 mm

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

Source of wave front

None of these

Source of secondary wave front

Source

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

Origin

Producer

Source

Base

74. Huygen’s wave theory of light cannot explain

Interference

Polarization

Photoelectric effect

Diffraction

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

Distance between the slits

Fringe width

Intensity ratio of the sources

Wavelength

Page 4 of 4

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

Band emission spectrum

Band absorption spectrum

Line emission spectrum

Line absorption spectrum

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

Of same amplitude

Be close to each other

Be narrow

Have constant phase difference

78. The setting of Newton’s rings is

None of these

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

A Plano convex lens and simple glass sheet

A Plano convex lens and the plane glass plate

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

Wavelength

Phase

Frequency

All of these

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

Interference

Diffraction

None of these

Doppler’s effect

81. 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

82. 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 10¹¹ to 5 x 10¹⁴ Hz

5 x 10⁵ to 5 x 10⁵ Hz

83. Crystals of a material can behave as

Convex lens

Interferometer

Concave

Diffraction grating

84. A polarizer is used to

Produce unpolarised light

Reduced intensity of light

Increase intensity of light

Produce polarized light

85. 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 of the wave

Speed of propagation greater than wave

86. 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

Diffraction pattern

Total internal reflection of light

Interference pattern produced due to thin oil film

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

A ray

Vibrator

Wave front

A half-period zone

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

Reflection

Refraction

Diffraction

Transmission

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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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