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ECAT Physics Optics Chapter Test Online

Mustansar KhanLast Updated: April 18, 2025

Physics Optics Chapter MCQS Online Test

ECAT Physics Electronics Chapter Online Test

Total Questions:	136
Time Allowed:	60 Minutes
Total Marks:	136
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ECAT Physics Optics Chapter Online Test

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Page 1 of 6

Physics

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

0.2

0.5

2. Ray optics is valid, when characteristic dimensions are

Of the order of one millimeter

Much smaller than the wavelength of length

Of the same order as the wavelength of light

Much larger than the wavelength of light

3. 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

2λ = dm

λ = 2d/m

λ = 2π dm

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

Of difference frequencies

White light

Coherent

Added

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

Line spectrum

Continuous emission spectrum

All of these

Emission spectrum

6. Geometrical optics cannot give following characteristics for a microscope

Resolution of image

Image position

Image size

Any of the above

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

None

Convex

Concave

Plane

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

Wavelength

Distance between the slits

Fringe width

Intensity ratio of the sources

9. 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 reduced in image

Intensity of image will be decreased

Housefly will be seen enlarged in image

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

Cannot be diffracted

Do not affect a photographic plate

Cannot be polarized

Have a lower frequency

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

None of these

Dark fringes are thicker than bright

Equal width

Different width

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

Incoherent

Electromagnetic

In the form of a narrow beam

Monochromatic

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

Equal to that of the eye piece

Greater than that of eye piece

Five times shorter than that of eye piece

Shorter than that of eye piece

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

Emission spectrum

Continuous emission spectrum

Line spectrum

All of these

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

Image is formed at - ∞ and is real

Image is formed at + ∞ and is virtual

Image is formed at + ∞ and is real

Image is formed at - ∞ and is virtual

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

4 times

½ times

2 times

¼ times

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

None of these

Frequency

Amplitude

Wavelength

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

Principal focus of the lens

Pole of the lens

Radius of curvature of the lens

Aperture of the lens

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

Of two different frequencies

Monochromatic

Coming from opposite direction

Of high intensity

20. The power of a concave lens is

Negative

Virtual

Positive

Real

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

A half-period zone

A ray

Wave front

Vibrator

22. The cause of mirage observed in desert is

Reflection

Total internal reflection

Scattering

Refraction

23. 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

5 m

50 m

1 m

10 m

24. Wavelength of light of frequency 100 Hz is

2 x 10⁶ m

4 x 10⁶ m

3 x 10⁶ m

5 x 10⁶ m

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

Sun light

Infrared

Sodium light

Page 2 of 6

26. The revolving power of a lens is given by

αmin = 1.22 D/λ

αmin = 1.28 D/λ

αmin = 1.21 λ/D

αmin = 1.22 λ/D

27. 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

28. In a simple microscope lens used is _________.

Biconvex

Cylindrical

Plano convex

Biconcave

29. 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

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

Reflection

Interference

Refraction

Diffraction

31. 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

None of these

Speed of propagation greater than wave

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

Interference pattern produced due to thin oil film

Total internal reflection of light

Polarization

Diffraction pattern

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

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

Beyond 2 f

Between principal focus and center of curvature

At the principal focus

Between principal focus and optical center

35. 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

Water to glass

Glass to water

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

d sin θ = (m + 1/2)²

d sin θ = (m + 1)²

d sin θ = (m + 1/2)

d sin θ = (m + 1/2)⁴

37. 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

5.5 x 10⁵

4.5 x 10⁸ cm

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

Diffraction

Reflection

Refraction

Dispersion

39. 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

25°

100°

10°

50°

40. There is no noticeable boundary between core and cladding

Multi-mode step index fiber

Multi-mode graded index fiber

All types of fiber

Single mode step index fiber

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

Energy of different colors is different

Phase of different colors is different

Velocity of different colors is different

Amplitude of different colors is different

42. Which does not show polarization?

Longitudinal waves in gas

Both A and B

None of these

Transverse wave in gas

43. A polarizer is used to

Reduced intensity of light

Produce polarized light

Increase intensity of light

Produce unpolarised light

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

Diodes

Laser

Repeaters

Transformer

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

25 cm and infinity

0 and infinity

25 cm and 100 cm

0 and 25 cm

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

Base

Source

Producer

Origin

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

Total internal reflection

Refraction

Reflection

Dispersion of light

48. Optic fibers are related with

Computer

None of these

Communication

Light

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

Increases

Remains unchanged

Gets halved

Decreases

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

Page 3 of 6

51. Final image produced by a compound microscope is

Virtual and inverted

Real and inverted

Real and erect

Virtual and erect

52. 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 graded index fiber

Multi-mode step index fiber

Single mode step index fiber

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

Aperture

Optical center

Center of curvature

Focus

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

Infinity

The least distance of the distinct vision

The focus of the objective lens

The focal of the eye piece

55. 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

56. Unit of power of a lens is

Horsepower

Diopter

Meter

Watt

57. Magnification of the astronomical telescope is

(1+fo/fe)L/fo

fo+fe

fe/fo

fo/fe

58. 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

6 cm

4.8 cm

3 cm

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

One (1)

Zero (0)

Neither zero (0) nor one (1)

Both zero (0) and one (1)

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

Refractive angle

Incidence angle

Deviation angle

Critical angle

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

Interference

Diffraction

Refraction

Reflection

62. 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

Increasing the distance between the slits

Using monochromatic light of higher frequency

Using monochromatic light of longer wavelength

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

Yellow

Red

Blue

Green

64. Magnifying power of simple microscope

Increase with increase in focal length

List distance of distinct vision

No effect with decrease or increase with focal length

Increase with decrease in focal length

65. Which of the following has least wavelength?

Ultra-violet rays

Cosmic-rays

ϒ-rays

X-rays

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

Virtual

Real and inverted

Real and erect

Virtual and erect

67. 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

68. 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 10⁵ to 5 x 10⁸ Hz

5 x 10⁸ to 5 x 10¹¹ Hz

5 x 10¹¹ to 5 x 10¹⁴ Hz

5 x 10¹⁴ to 5 x 10¹⁷ Hz

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

Of same frequency

Different wavelength

Of the same frequency and having definite phase relationship

Of nearly the same frequency

70. The diameter of a lens is called

Aperture

Principal axis

Focal length

Radius of curvature

71. 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

72. 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

Intensity of image will be decreased

Housefly will be seen reduced in image

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

.m Sin θ = (d + ½)λ

.d Sin θ = (m + ½)λ

½ d Sin θ = mλ

2π Sin θ = (m + ½)λ

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

Line spectrum

Discontinuous spectrum

Band spectrum

Continuous spectrum

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

Plano-convex

Double-convex

Plano-concave

Convexo-concave

Page 4 of 6

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

Turn table

Telescope

All of these

Collimator

77. Wavelength of light of frequency 100 Hz is

5 x 10⁶ m

4 x 10⁶ m

3 x 10⁶ m

2 x 10⁶ m

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

R = m/N

R = N/m

R = N x m

R = N x m²

79. 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

None of these

Decreasing gradually

Increasing gradually

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

Same

Zero

Different

Different with refractive index of core higher than cladding

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

λD/2d

λD/4d

2λD/d

λD/d

82. For the normal setting of a telescope

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

Only the object is at infinity

Both the object and the final image is at infinity

Only the final image is at infinity

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

25l

16l

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

Diffraction

Origin of spectra

Refraction

Reflection

85. 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

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

Parabolic

Elliptical

Straight

Circular

87. Soap bubble looks colored due to

Interference

Reflection

Any one of these

Dispersion

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

Band emission spectrum

Line emission spectrum

Band absorption spectrum

Line absorption spectrum

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

Concave

None

Convex

Plane

90. Choose the correct statement

Rays may be normal to wave front

There is no relationship between rays and wave fronts

Rays are normal to wave front

Rays are not normal to wave front

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

Parallel

Equal

Perpendicular

Opposite

92. Geometrical optics cannot give following characteristics for a microscope

Image position

Any of the above

Resolution of image

Image size

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

1/10 diopter

10 diopter

2/10 diopter

11 diopter

94. 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 not absorbed

Laser rays are high velocity waves

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

3 meters

4 meters

1 meter

2 meters

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

Refraction

Dispersion

Scattering

Reflection

97. In a compound microscope, the intermediate image is

Virtual, inverted and magnified

Virtual, erect and magnified

Virtual, erect and reduced

Real, erect and magnified

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

Virtual and inverted

Virtual and Erect

Real and inverted

Real and Erect

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

240

260

280

200

100. Resolving power of a telescope depends on:

Diameter of objective lens

The magnification of eyepiece

The focal length of objective lens

Refractive index of objective lens

Page 5 of 6

101. For constructive interference the path difference is

mλ

m²λ

½ mλ

(m – 1) λ

102. Choose the correct statement

Rays are not normal to wave front

Rays are normal to wave front

Raya may be normal to wave front

There is no relationship between rays and wave fronts

103. Resolving power of a telescope depends on:

The focal length of objective lens

Diameter of objective lens

The magnification of eyepiece

Refractive index of objective lens

104. The fringe spacing in case of blue light

Increases

None of these

Remains the same

Decrease

105. Inverse square law for luminance is valid for

Cylindrical source

All types of sources

Search light

Isotropic point source

106. 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

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

Optical fibers are subject to electromagnetic interference from outside

Optical fibers may have homogeneous core with a suitable cladding

Optical fibers have extremely low transmission loss

Optical fibers can be of graded refractive index

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

Electromagnetic

Monochromatic

In the form of a narrow beam

Incoherent

109. 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

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

Y = (m+1/2) dL/λ

Y = (m+1/2)λL/d

Y = (m+1/2)λd/L

Y = (m+1)λL/d

111. Which is having minimum wavelength?

ϒ-rays

Cosmic-rays

X-rays

Ultra-violet rays

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

113. 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

Infinite

Larger

None of these

Smaller

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

Amplitude

Intensity

Energy

Momentum

115. 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 glass

Water to air

Glass to air

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

Velocity

Frequency

Amplitude

Wavelength

117. 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

3.5 cm

2 cm

3 cm

118. What is the most important function of telescope?

Resolution

None of these

Light collection

Magnification

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

½ mλ

(m – 1/2)λ

(m + 1/2)λ

mλ

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

If the object is with in C

Both b and c

Object is beyond C

If the object is within f

121. 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

Halved

Doubled

Quadrupled

Unchanged

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

Orange

Violet

Red

Green

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

Supersonics

Sound

Light

Ultrasonics

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

Plano concave lens

Converging (or convex) lens

Plano convex lens

Diverging (or concave) lens

125. Inverse square law for luminance is valid for

All types of sources

Isotropic point source

Search light

Cylindrical source

Page 6 of 6

126. The cause of mirage observed in desert is

Total internal reflection

Refraction

Scattering

Reflection

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

Chromatic aberration as well as spherical aberration

Chromatic aberration

All of the above

Spherical aberration

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

Infinity

The focal of the eye piece

The focus of the objective lens

The least distance of the distinct vision

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

Zero

Minimum

None of these

Maximum

130. Which part of the spectrum is most visible?

Yellow-green

Violet

Red

Yellow

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

Laser rays are not absorbed

Laser rays are most coherent waves

Laser rays are high velocity waves

Laser rays propagate in a straight line

132. In a compound microscope, the intermediate image is

Virtual, erect and reduced

Virtual, erect and magnified

Real, erect and magnified

Virtual, inverted and magnified

133. 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

15 cm

10 cm

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

3 times

9 times

1/9 times

1/3 times

135. 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

None of these

Interference

Police

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

Band emission spectrum

Line emission spectrum

Line absorption spectrum

Band absorption spectrum

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Mustansar KhanLast Updated: April 18, 2025

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ECAT Physics Optics Chapter Test Online

Physics Optics Chapter MCQS Online Test

ECAT Physics Electronics Chapter Online Test

ECAT Physics Optics Chapter Online Test

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Physics Optics Chapter MCQS Online Test

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