Physics Optics Online Mcqs Test

Mustansar KhanLast Updated: October 13, 2025

Important Electronics Question and Answer

Total Questions:	136
Time Allowed:	60 Minutes
Total Marks:	136
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Physics Optics Practice Test Online With Explanation

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Page 1 of 6

Physics

1. A point where the incident parallel rays of light converge or appear to diverge after passing through a lens is called

Focus

Aperture

Optical center

Center of curvature

2. There is no noticeable boundary between core and cladding

Single mode step index fiber

All types of fiber

Multi-mode step index fiber

Multi-mode graded index fiber

3. The electrical signals change into light signals for transmission through optical fiber. A light pulse represent

Both zero (0) and one (1)

Zero (0)

Neither zero (0) nor one (1)

One (1)

4. If the focal length of objective is 10 mm find its magnification

5. Optic fibers are related with

Computer

Light

Communication

None of these

6. Image of an object 5 mm high is only 1 cm high, Magnification produced by lens is

0.5

0.2

7. In astronomical telescope the final image for normal vision is formed at

The least distance of the distinct vision

Infinity

The focus of the objective lens

The focal of the eye piece

8. In optic fiber transmission system ________ are used regenerate the dim light signal.

Laser

Transformer

Diodes

Repeaters

9. For constructive interference the path difference is

m²λ

mλ

(m – 1) λ

½ mλ

10. The resolving power of telescope depends on

Focal length of eye lens

Focal length of objective lens

Length of the telescope

Diameter of the objective lens

11. An object is placed between f and 2f of a concave lens. The image formed will formed will be

Real and Erect

Virtual and inverted

Real and inverted

Virtual and Erect

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

Electromagnetic

In the form of a narrow beam

Monochromatic

Incoherent

13. The critical angle for a ray of light suffering total internal reflection will be smallest for the ray traveling from

Glass to water

Water to air

Glass to air

Water to glass

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

Y = (m+1/2) dL/λ

Y = (m+1)λL/d

Y = (m+1/2)λL/d

Y = (m+1/2)λd/L

15. A ________ lens is used to form Newton’s rings:

Double-convex

Plano-concave

Plano-convex

Convexo-concave

16. Geometrical optics cannot give following characteristics for a microscope

Resolution of image

Image size

Image position

Any of the above

17. In a compound microscope, the intermediate image is

Virtual, erect and magnified

Real, erect and magnified

Virtual, erect and reduced

Virtual, inverted and magnified

18. The power of a concave lens is

Positive

Negative

Real

Virtual

19. When the object is placed at 2f of a convex lens then the image formed behind the lens will be

At 2f

At the focus

Between f and 2 f

Beyond 2f

20. Which of the following is a part of spectrometer?

All of these

Collimator

Turn table

Telescope

21. 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

Polarization

Total internal reflection of light

Diffraction pattern

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

Speed of propagation of the wave

Speed of propagation less than the wave

Speed of propagation greater than wave

None of these

23. The setting of Newton’s rings is

None of these

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

24. A telescope has an objective lens of focal length 1.5m and an eye piece of focal length 5 cm. IF this telescope is used in normal setting to view a tower of height 100m located 3km away, what will be the height of the image of the tower?

25 cm

15 cm

20 cm

10 cm

25. The diameter of a lens is called

Radius of curvature

Focal length

Aperture

Principal axis

Page 2 of 6

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

Line spectrum

Emission spectrum

Continuous emission spectrum

All of these

27. Finger prints on paper are identified by sprinkling fluorescent powder on it and observing it under

Infrared

Sun light

Sodium light

28. Which does not show polarization?

None of these

Both A and B

Longitudinal waves in gas

Transverse wave in gas

29. If the magnification M₁ = 20.0 for objective and M₂ = 12.0 then total magnification is

240

200

260

280

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

2π Sin θ = (m + ½)λ

.m Sin θ = (d + ½)λ

½ d Sin θ = mλ

.d Sin θ = (m + ½)λ

31. The focal lengths of the eye piece and objective of a telescope are respectively 100 cm and 2 cm. The moon subtends an angle of 0.5° at the eye. If it is looked through the telescope, the angle subtended by the moon’s image will be

10°

50°

25°

100°

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

Decreasing gradually

It is constant at the center

Increasing gradually

None of these

33. 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

Doppler’s effect

Interference

34. Resolving power of a telescope depends on:

The focal length of objective lens

Refractive index of objective lens

Diameter of objective lens

The magnification of eyepiece

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

Diffraction

Reflection

Refraction

Interference

36. To get the position of the image of an object at least how many rays emerging from any point of the object are required?

37. In Young’s double slit experiment, the separation between the slit is halved and distance between the slit and screen is doubled. The fringe width is

Doubled

Quadrupled

Halved

Unchanged

38. In a compound microscope, the intermediate image is

Real, erect and magnified

Virtual, inverted and magnified

Virtual, erect and reduced

Virtual, erect and magnified

39. The cause of mirage observed in desert is

Total internal reflection

Scattering

Reflection

Refraction

40. In compound microscope, length of microscope is 21.5 cm, focal length of objective is 1.6 cm, focal length of eye piece is 2.1 cm and if final image is formed at infinity they distance of object from objective lens is

1.9 cm

4.8 cm

6 cm

3 cm

41. A spectrometer is an optical device used to study the spectra from different sources of light which is

None of these

fₒ - fₑ

fₑ - fₒ

fₑ + fₒ

42. The direction of a ray of light is _________ to the wave front.

Opposite

Parallel

Perpendicular

Equal

43. Which one type of fiber is more suitable for transmission of signals in which white light is used?

Multi-mode step index fiber

Single mode step index fiber

Multi-mode graded index fiber

Mono mode step index fiber

44. If the red light is replaced by blue light illuminating the object in a microscope the resolving power of the microscope

Gets halved

Decreases

Remains unchanged

Increases

45. At what distance should a book be placed from a 50 cd bulb so that the luminance on the book becomes 2 lm m¯²

1 m

5 m

10 m

50 m

46. Soap bubble looks colored due to

Any one of these

Reflection

Interference

Dispersion

47. The critical angle for a ray of light suffering total internal reflection will be smallest for the ray traveling from

Glass to air

Glass to water

Water to glass

Water to air

48. In Young’s double slit experiment, the separation between the slits is made 3 fold, the fringe width becomes

1/9 times

9 times

1/3 times

3 times

49. Resolving power of a telescope depends on:

Refractive index of objective lens

The magnification of eyepiece

Diameter of objective lens

The focal length of objective lens

50. In the phenomenon of interference, the bright and dark fringes are of

Equal width

Dark fringes are thicker than bright

Different width

None of these

Page 3 of 6

51. The diameter of a lens under use is called the

Radius of curvature of the lens

Principal focus of the lens

Pole of the lens

Aperture of the lens

52. The cause of mirage observed in desert is

Total internal reflection

Scattering

Refraction

Reflection

53. For interference to occur, the two light waves should be:

Coming from opposite direction

Monochromatic

Of two different frequencies

Of high intensity

54. In a astronomical telescope the final image for normal vision is formed at

The least distance of the distinct vision

The focus of the objective lens

Infinity

The focal of the eye piece

55. If an object is placed away from 2f of a converging lens then the image will be

Virtual and erect

Real and inverted

Virtual

Real and erect

56. Consider telecommunication through optical fibers. Which of the following statements is not true?

Optical fibers may have homogeneous core with a suitable cladding

Optical fibers can be of graded refractive index

Optical fibers are subject to electromagnetic interference from outside

Optical fibers have extremely low transmission loss

57. For obtaining equal and same height of the image, mirror used should be

None

Concave

Plane

Convex

58. While viewing a distant object with a telescope suddenly a housefly sits on objective lens. The correct statement is that

Intensity of image will be decreased

Intensity of image will be increased

Housefly will be seen reduced in image

Housefly will be seen enlarged in image

59. Magnifying power of simple microscope

Increase with decrease in focal length

No effect with decrease or increase with focal length

List distance of distinct vision

Increase with increase in focal length

60. A polarizer is used to

Produce unpolarised light

Produce polarized light

Increase intensity of light

Reduced intensity of light

61. Which of the following features determines the resolving power of telescope?

The focal length of eyepiece

The focal length of the objective

The diameter of the objective

Two of the above

62. Critical angle of light passing from glass to air is minimum for

Yellow

Red

Green

Blue

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

Momentum

Amplitude

Energy

Intensity

64. For the normal setting of a telescope

Only the object is at infinity

Only the final image is at infinity

Both the object and the final image is at infinity

Neither the object nor the final image has to be at infinity

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

Laser rays are high velocity waves

Laser rays are not absorbed

Laser rays propagate in a straight line

Laser rays are most coherent waves

66. In Newton’s rigs the point of contact of the lens and the glass plate, the air film is

Zero

Maximum

Minimum

None of these

67. What is the main cayuse of the shining of diamond?

Dispersion of light

Refraction

Total internal reflection

Reflection

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

Distance between the slits

Wavelength

Intensity ratio of the sources

Fringe width

69. In multimode step index fiber the refractive index of core and cladding is

Different

Same

Zero

Different with refractive index of core higher than cladding

70. 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?

Increasing the distance between the slits

Using monochromatic light of longer wavelength

Decreasing the distance between the screen and the slits

Using monochromatic light of higher frequency

71. Just before setting, the sun may appear to be elliptical. This happens due to

Diffraction

Refraction

Dispersion

Reflection

72. Power of a lens is one diopter if its focal length is

1 meter

2 meters

4 meters

3 meters

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

25l

16l

74. If the distance of a surface from light source is doubled, then the luminance will become

2 times

¼ times

4 times

½ times

75. In a simple microscope lens used is _________.

Cylindrical

Biconcave

Plano convex

Biconvex

Page 4 of 6

76. A beam of light enters air from water. Which of the following characteristics of light will not change in water?

Frequency

Velocity

Amplitude

Wavelength

77. The speed of light in vacuum is 3 x 10⁵ ms¯¹. Its speed in a medium of refractive index 1.5 will be

5.5 x 10⁵

6.5 x 10⁸

2 x 10⁵ ms¯¹

4.5 x 10⁸ cm

78. If f = 5 cm and d = 25 cm then the magnification will be

79. The revolving power of a lens is given by

αmin = 1.21 λ/D

αmin = 1.22 λ/D

αmin = 1.22 D/λ

αmin = 1.28 D/λ

80. A lens which converges a beam of parallel rays to a point is called

Plano convex lens

Plano concave lens

Converging (or convex) lens

Diverging (or concave) lens

81. The resolving power of a telescope depends on

The ratio of the focal length and the diameter

Its diameter (of the objective)

Its magnification

Its focal length

82. What is the most important function of telescope?

Magnification

Resolution

None of these

Light collection

83. The inability of the lens to focus all the dispersed colors at one point is called

Spherical aberration

Chromatic aberration as well as spherical aberration

All of the above

Chromatic aberration

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

Cannot be diffracted

Cannot be polarized

Do not affect a photographic plate

Have a lower frequency

85. The astronomical telescope consists of objective and eye piece. The focal length of the objective is

Shorter than that of eye piece

Equal to that of the eye piece

Greater than that of eye piece

Five times shorter than that of eye piece

86. A convex lens has focal length F. An object is placed at F then

Image is formed at + ∞ and is virtual

Image is formed at + ∞ and is real

Image is formed at - ∞ and is real

Image is formed at - ∞ and is virtual

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

Energy of different colors is different

Amplitude of different colors is different

Phase of different colors is different

Velocity of different colors is different

88. The fringe spacing in case of blue light

Decrease

Increases

None of these

Remains the same

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

Line absorption spectrum

Band emission spectrum

Band absorption spectrum

Line emission spectrum

90. The difference between 1st ring fringe and 1st dark fringe is measured as

λD/2d

λD/4d

λD/d

2λD/d

91. 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

2λ = dm

λ = 2π dm

92. For destructive interference, the path difference is give by:

½ mλ

mλ

(m + 1/2)λ

(m – 1/2)λ

93. Wavelength of light of frequency 100 Hz is

4 x 10⁶ m

5 x 10⁶ m

3 x 10⁶ m

2 x 10⁶ m

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

d sin θ = (m + 1/2)

d sin θ = (m + 1/2)⁴

d sin θ = (m + 1/2)²

d sin θ = (m + 1)²

95. The length of a microscope is 12 cm and its magnifying power is 25 for relaxed eye. The focal length of the eye piece is 4 cm. The distance of the object from the objective is

3.5 cm

3 cm

2 cm

2.5 cm

96. Diopter power of an concave lens of 10 cm focal length is

10 diopter

11 diopter

1/10 diopter

2/10 diopter

97. Final image produced by a compound microscope is

Real and inverted

Virtual and inverted

Real and erect

Virtual and erect

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

Laser rays propagate in a straight line

Laser rays are not absorbed

Laser rays are high velocity waves

Laser rays are most coherent waves

99. The apparent size of an object depends on the angle subtended but it at the eye. As the angle increases the size of the object

Smaller

None of these

Infinite

Larger

100. Inverse square law for luminance is valid for

Isotropic point source

Cylindrical source

Search light

All types of sources

Page 5 of 6

101. Ray optics is valid, when characteristic dimensions are

Much larger than the wavelength of light

Of the order of one millimeter

Much smaller than the wavelength of length

Of the same order as the wavelength of light

102. While viewing a distant object with a telescope suddenly a housefly sits on objective lens. The correct statement is that

Housefly will be seen enlarged in image

Housefly will be seen reduced in image

Intensity of image will be increased

Intensity of image will be decreased

103. A convex lens acts as a diverging lens if the

Object is beyond C

Both b and c

If the object is with in C

If the object is within f

104. Wavelength of light of frequency 100 Hz is

2 x 10⁶ m

5 x 10⁶ m

3 x 10⁶ m

4 x 10⁶ m

105. Which is having minimum wavelength?

ϒ-rays

Cosmic-rays

Ultra-violet rays

X-rays

106. Which of the following has least wavelength?

ϒ-rays

X-rays

Cosmic-rays

Ultra-violet rays

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

Refraction

Diffraction

Origin of spectra

Reflection

108. For obtaining equal and same height, mirror should be

Convex

Concave

Plane

None

109. A convex lens gives a virtual image only when the objects lies

Between principal focus and center of curvature

Between principal focus and optical center

At the principal focus

Beyond 2 f

110. Which part of the spectrum is most visible?

Red

Yellow

Yellow-green

Violet

111. Which of the following spectrum have all the frequencies from high to low frequency range?

Discontinuous spectrum

Band spectrum

Continuous spectrum

Line spectrum

112. Unit of power of a lens is

Diopter

Watt

Horsepower

Meter

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

Refraction

Diffraction

Interference

Reflection

114. A double convex lens acts as a diverging lens when the object is

All of these

Inside the focus

At the focus

Between f and 2f

115. Magnification of the astronomical telescope is

fe/fo

(1+fo/fe)L/fo

fo/fe

fo+fe

116. When at some angle of incidence, the angle of reflection is equal to 90°. This angle is called

Incidence angle

Refractive angle

Critical angle

Deviation angle

117. 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 10¹¹ to 5 x 10¹⁴ Hz

5 x 10⁸ to 5 x 10¹¹ Hz

5 x 10⁵ to 5 x 10⁸ Hz

118. If N is the number of rulings on the grating, then the resolving power in the mth order diffraction equals to

R = N x m²

R = N/m

R = m/N

R = N x m

119. The separation between successive fringes in a double slit arrangement is x. If the whole arrangement is dipped under water what will be the new fringe separation? [The wavelength of light being used is 5000 A]

1.5 x

0.83x

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

Of nearly the same frequency

Of the same frequency and having definite phase relationship

Different wavelength

Of same frequency

121. Near and far points of a healthy human eye respectively are

25 cm and 100 cm

25 cm and infinity

0 and 25 cm

0 and infinity

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

A ray

Vibrator

A half-period zone

Wave front

123. For interference to occur, the interfering beams of light must be

White light

Added

Of difference frequencies

Coherent

124. Inverse square law for luminance is valid for

All types of sources

Isotropic point source

Cylindrical source

Search light

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

Producer

Source

Base

Origin

Page 6 of 6

126. Signal form a remote control to the device operated by it travels with the speed of:

Ultrasonics

Sound

Supersonics

Light

127. Geometrical optics cannot give following characteristics for a microscope

Any of the above

Image size

Image position

Resolution of image

128. Choose the correct statement

Rays are normal to wave front

Raya may be normal to wave front

Rays are not normal to wave front

There is no relationship between rays and wave fronts

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

Circular

Straight

Elliptical

Parabolic

130. Sun has elliptical shape, when it rises and sets due to

Refraction

Scattering

Dispersion

Reflection

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

All of these

Continuous emission spectrum

Line spectrum

Emission spectrum

132. Choose the correct statement

There is no relationship between rays and wave fronts

Rays are not normal to wave front

Rays are normal to wave front

Rays may be normal to wave front

133. The velocity of light in vacuum can be changed by changing

Wavelength

Frequency

None of these

Amplitude

134. Which of the following wavelengths will suffer maximum deviation while passing through a prism?

Orange

Violet

Red

Green

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

Monochromatic

Electromagnetic

Incoherent

In the form of a narrow beam

Police

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

Band absorption spectrum

Line absorption spectrum

Band emission spectrum

Line emission spectrum

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