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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. In a simple microscope lens used is _________.

Biconcave

Cylindrical

Biconvex

Plano convex

2. The power of a concave lens is

Real

Negative

Positive

Virtual

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

Chromatic aberration as well as spherical aberration

Spherical aberration

Chromatic aberration

All of the above

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

Diffraction

Reflection

Refraction

Interference

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

6.5 x 10⁸

2 x 10⁵ ms¯¹

4.5 x 10⁸ cm

5.5 x 10⁵

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

Added

Of difference frequencies

White light

Coherent

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

11 diopter

10 diopter

2/10 diopter

1/10 diopter

8. Magnifying power of simple microscope

Increase with decrease in focal length

Increase with increase in focal length

List distance of distinct vision

No effect with decrease or increase with focal length

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

Of high intensity

Monochromatic

Coming from opposite direction

Of two different frequencies

10. Which of the following has least wavelength?

Ultra-violet rays

ϒ-rays

X-rays

Cosmic-rays

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

Perpendicular

Parallel

Opposite

Equal

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

Phase of different colors is different

Amplitude of different colors is different

Velocity of different colors is different

Energy of different colors is different

13. Unit of power of a lens is

Horsepower

Meter

Watt

Diopter

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

Reflection

Dispersion of light

Total internal reflection

Refraction

15. 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

Intensity of image will be decreased

Intensity of image will be increased

Housefly will be seen reduced in image

16. The diameter of a lens is called

Radius of curvature

Principal axis

Aperture

Focal length

17. Which does not show polarization?

Transverse wave in gas

Both A and B

Longitudinal waves in gas

None of these

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

Optical center

Center of curvature

Focus

Aperture

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

25l

16l

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

In the form of a narrow beam

Monochromatic

Electromagnetic

Incoherent

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

Diffraction

Refraction

Dispersion

Reflection

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

Base

Source

Producer

Origin

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

2π Sin θ = (m + ½)λ

.d Sin θ = (m + ½)λ

.m Sin θ = (d + ½)λ

½ d Sin θ = mλ

24. For the normal setting of a telescope

Only the object 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

Only the final image is at infinity

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

Have a lower frequency

Do not affect a photographic plate

Cannot be polarized

Cannot be diffracted

Page 2 of 6

26. 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?

20 cm

25 cm

10 cm

15 cm

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

Object is beyond C

If the object is with in C

If the object is within f

Both b and c

28. What is the most important function of telescope?

Magnification

Light collection

None of these

Resolution

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

Frequency

Amplitude

None of these

Wavelength

30. The revolving power of a lens is given by

αmin = 1.28 D/λ

αmin = 1.22 λ/D

αmin = 1.22 D/λ

αmin = 1.21 λ/D

31. In a compound microscope, the intermediate image is

Virtual, erect and reduced

Virtual, inverted and magnified

Virtual, erect and magnified

Real, erect and magnified

32. Inverse square law for luminance is valid for

All types of sources

Search light

Isotropic point source

Cylindrical source

33. The cause of mirage observed in desert is

Refraction

Reflection

Total internal reflection

Scattering

34. 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 = 2d/m

λ = 2π dm

2λ = dm

λ = dm

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

Sun light

Infrared

Sodium light

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

Water to air

Glass to air

Glass to water

Water to glass

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

Frequency

Wavelength

Amplitude

Velocity

38. 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

Using monochromatic light of longer wavelength

Decreasing the distance between the screen and the slits

Increasing the distance between the slits

39. The fringe spacing in case of blue light

Increases

None of these

Decrease

Remains the same

40. Which part of the spectrum is most visible?

Yellow-green

Red

Violet

Yellow

41. Ray optics is valid, when characteristic dimensions are

Of the order of one millimeter

Of the same order as the wavelength of light

Much smaller than the wavelength of length

Much larger than the wavelength of light

42. Soap bubble looks colored due to

Any one of these

Interference

Dispersion

Reflection

43. 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

44. 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

Polarization

Interference pattern produced due to thin oil film

45. In a compound microscope, the intermediate image is

Virtual, erect and magnified

Virtual, erect and reduced

Virtual, inverted and magnified

Real, erect and magnified

46. 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

None of these

Infinite

Larger

Smaller

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

260

240

280

200

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

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

λD/4d

λD/2d

2λD/d

λD/d

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

Diffraction

Doppler’s effect

Interference

None of these

Page 3 of 6

51. 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]

0.83x

1.5 x

52. Geometrical optics cannot give following characteristics for a microscope

Any of the above

Image position

Resolution of image

Image size

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

Between f and 2f

At the focus

All of these

Inside the focus

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

Virtual and inverted

Real and inverted

Virtual and Erect

Real and Erect

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

½ mλ

(m – 1/2)λ

(m + 1/2)λ

mλ

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

Decreases

Remains unchanged

Gets halved

Increases

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

Yellow

Red

Blue

Green

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

Water to glass

Glass to air

Water to air

Glass to water

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

Continuous spectrum

Line spectrum

Band spectrum

Discontinuous spectrum

60. 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

61. 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

50 m

10 m

5 m

62. The resolving power of a telescope depends on

Its diameter (of the objective)

The ratio of the focal length and the diameter

Its magnification

Its focal length

63. Final image produced by a compound microscope is

Real and erect

Virtual and inverted

Real and inverted

Virtual and erect

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

Line spectrum

Continuous emission spectrum

Emission spectrum

All of these

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

Laser rays are most coherent waves

Laser rays are not absorbed

Laser rays propagate in a straight line

Laser rays are high velocity waves

66. The resolving power of telescope depends on

Diameter of the objective lens

Focal length of eye lens

Length of the telescope

Focal length of objective lens

67. 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

3 cm

1.9 cm

6 cm

4.8 cm

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

Line emission spectrum

Band absorption spectrum

Line absorption spectrum

Band emission spectrum

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

None

Concave

Convex

Plane

70. 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+1/2) dL/λ

Y = (m+1)λL/d

71. 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

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

Equal to that of the eye piece

Five times shorter than that of eye piece

Greater than that of eye piece

Shorter than that of eye piece

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

Diverging (or concave) lens

Plano convex lens

Plano concave lens

Converging (or convex) lens

74. Choose the correct statement

Rays are normal to wave front

Rays are not normal to wave front

There is no relationship between rays and wave fronts

Raya may be normal to wave front

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

Increasing gradually

None of these

It is constant at the center

Decreasing gradually

Page 4 of 6

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

Plano-concave

Plano-convex

Convexo-concave

Double-convex

77. Wavelength of light of frequency 100 Hz is

3 x 10⁶ m

4 x 10⁶ m

5 x 10⁶ m

2 x 10⁶ m

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

The least distance of the distinct vision

The focal of the eye piece

Infinity

The focus of the objective lens

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

Collimator

Telescope

Turn table

All of these

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

Emission spectrum

All of these

Line spectrum

Continuous emission spectrum

81. 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

82. 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 increased

Housefly will be seen enlarged in image

Housefly will be seen reduced in image

Intensity of image will be decreased

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

Energy

Intensity

Momentum

Amplitude

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

Between principal focus and optical center

Beyond 2 f

Between principal focus and center of curvature

At the principal focus

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

Reflection

Refraction

Diffraction

Interference

86. A polarizer is used to

Reduced intensity of light

Increase intensity of light

Produce polarized light

Produce unpolarised light

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

Mono mode step index fiber

Multi-mode step index fiber

Single mode step index fiber

Multi-mode graded index fiber

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

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

Repeaters

Transformer

Laser

Diodes

90. 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

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

Speed of propagation less than the wave

None of these

Speed of propagation of the wave

Speed of propagation greater than wave

92. 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 x m

R = N/m

R = m/N

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

Both zero (0) and one (1)

One (1)

Neither zero (0) nor one (1)

Zero (0)

94. Magnification of the astronomical telescope is

fe/fo

fo+fe

fo/fe

(1+fo/fe)L/fo

95. 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

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

Fringe width

Wavelength

Intensity ratio of the sources

Distance between the slits

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

The focus of the objective lens

The least distance of the distinct vision

The focal of the eye piece

Infinity

98. Optic fibers are related with

Communication

Light

None of these

Computer

99. Geometrical optics cannot give following characteristics for a microscope

Resolution of image

Any of the above

Image size

Image position

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

Same

Zero

Different with refractive index of core higher than cladding

Different

Page 5 of 6

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

Monochromatic

Incoherent

Electromagnetic

In the form of a narrow beam

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

0.5

0.2

103. 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°

25°

50°

100°

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

Dispersion

Scattering

Reflection

Refraction

105. 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

2.5 cm

2 cm

3.5 cm

3 cm

106. 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

107. 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

108. 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

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

Parabolic

Straight

Elliptical

Circular

110. 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 10⁸ to 5 x 10¹¹ Hz

5 x 10⁵ to 5 x 10⁸ Hz

5 x 10¹¹ to 5 x 10¹⁴ Hz

5 x 10¹⁴ to 5 x 10¹⁷ Hz

111. Which is having minimum wavelength?

ϒ-rays

Cosmic-rays

Ultra-violet rays

X-rays

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

1/3 times

1/9 times

3 times

9 times

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

1 meter

3 meters

4 meters

2 meters

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

None of these

Minimum

Zero

Maximum

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

Of nearly the same frequency

Different wavelength

Of the same frequency and having definite phase relationship

Of same frequency

116. Wavelength of light of frequency 100 Hz is

4 x 10⁶ m

2 x 10⁶ m

5 x 10⁶ m

3 x 10⁶ m

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

fₑ - fₒ

None of these

fₒ - fₑ

fₑ + fₒ

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

¼ times

2 times

4 times

½ times

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

120. Resolving power of a telescope depends on:

The magnification of eyepiece

The focal length of objective lens

Diameter of objective lens

Refractive index of objective lens

121. There is no noticeable boundary between core and cladding

Single mode step index fiber

Multi-mode graded index fiber

Multi-mode step index fiber

All types of fiber

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

Reflection

Refraction

Diffraction

Origin of spectra

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

Radius of curvature of the lens

Principal focus of the lens

Aperture of the lens

Pole of the lens

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

Real and erect

Virtual and erect

Virtual

Real and inverted

125. The cause of mirage observed in desert is

Refraction

Scattering

Total internal reflection

Reflection

Page 6 of 6

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

At 2f

Beyond 2f

At the focus

Between f and 2 f

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

Dark fringes are thicker than bright

Equal width

None of these

Different width

128. Inverse square law for luminance is valid for

Isotropic point source

Cylindrical source

Search light

All types of sources

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

Orange

Violet

Red

Green

130. For constructive interference the path difference is

m²λ

mλ

(m – 1) λ

½ mλ

131. 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

Unchanged

Halved

Quadrupled

Doubled

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

Plane

Concave

Convex

None

133. Resolving power of a telescope depends on:

The focal length of objective lens

The magnification of eyepiece

Diameter of objective lens

Refractive index of objective lens

134. 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 are subject to electromagnetic interference from outside

Optical fibers have extremely low transmission loss

Optical fibers can be of graded refractive index

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

Light

Sound

Supersonics

Ultrasonics

Police

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

Band absorption spectrum

Line absorption spectrum

Line emission spectrum

Band emission spectrum

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Mustansar KhanLast Updated: October 13, 2025

Physics Optics Online Mcqs Test

Important Electronics Question and Answer

Physics Optics Practice Test Online With Explanation

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