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

2 times

¼ times

½ times

4 times

2. 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 real

Image is formed at - ∞ and is virtual

Image is formed at + ∞ and is virtual

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

Same

Different with refractive index of core higher than cladding

Zero

Different

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

.m Sin θ = (d + ½)λ

2π Sin θ = (m + ½)λ

½ d Sin θ = mλ

.d Sin θ = (m + ½)λ

5. Ray optics is valid, when characteristic dimensions are

Much larger than the wavelength of light

Much smaller than the wavelength of length

Of the same order as the wavelength of light

Of the order of one millimeter

6. 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

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

Between principal focus and optical center

Between principal focus and center of curvature

At the principal focus

Beyond 2 f

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

Y = (m+1/2)λd/L

Y = (m+1)λL/d

Y = (m+1/2)λL/d

Y = (m+1/2) dL/λ

9. The cause of mirage observed in desert is

Reflection

Scattering

Refraction

Total internal reflection

10. Magnification of the astronomical telescope is

(1+fo/fe)L/fo

fe/fo

fo+fe

fo/fe

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

Beyond 2f

Between f and 2 f

At 2f

At the focus

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

Chromatic aberration

All of the above

Chromatic aberration as well as spherical aberration

Spherical aberration

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

Blue

Green

Red

Yellow

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

Zero

None of these

Maximum

Minimum

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

Distance between the slits

Fringe width

Wavelength

Intensity ratio of the sources

16. Soap bubble looks colored due to

Interference

Dispersion

Reflection

Any one of these

17. Resolving power of a telescope depends on:

The magnification of eyepiece

The focal length of objective lens

Refractive index of objective lens

Diameter of objective lens

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

fₑ + fₒ

fₒ - fₑ

fₑ - fₒ

None of these

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

Do not affect a photographic plate

Have a lower frequency

Cannot be polarized

Cannot be diffracted

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

Diffraction

Interference

Reflection

Refraction

21. Which of the following has least wavelength?

Ultra-violet rays

X-rays

ϒ-rays

Cosmic-rays

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

23. Wavelength of light of frequency 100 Hz is

2 x 10⁶ m

3 x 10⁶ m

4 x 10⁶ m

5 x 10⁶ m

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

Amplitude

Momentum

Intensity

Energy

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

None of these

Equal width

Different width

Dark fringes are thicker than bright

Page 2 of 6

26. 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

27. For the normal setting of a telescope

Only the final image is at infinity

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

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

2/10 diopter

11 diopter

10 diopter

1/10 diopter

29. Unit of power of a lens is

Watt

Meter

Diopter

Horsepower

30. 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

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

None of these

Frequency

Amplitude

Wavelength

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

λD/d

2λD/d

λD/2d

λD/4d

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

Opposite

Equal

Perpendicular

Parallel

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

If the object is with in C

Object is beyond C

If the object is within f

Both b and c

35. Final image produced by a compound microscope is

Virtual and erect

Real and inverted

Virtual and inverted

Real and erect

36. 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 increased

Housefly will be seen reduced in image

Intensity of image will be decreased

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

Amplitude

Velocity

Wavelength

Frequency

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

Laser rays are most coherent waves

Laser rays are not absorbed

Laser rays are high velocity waves

Laser rays propagate in a straight line

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

Sound

Light

Ultrasonics

Supersonics

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

Incoherent

Electromagnetic

Monochromatic

In the form of a narrow beam

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

Sodium light

Infrared

Sun light

42. 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

4.8 cm

1.9 cm

6 cm

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

Of two different frequencies

Of high intensity

Coming from opposite direction

Monochromatic

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

All of these

Collimator

Telescope

Turn table

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

Reflection

Refraction

Diffraction

Dispersion

46. The power of a concave lens is

Virtual

Negative

Real

Positive

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

Repeaters

Transformer

Diodes

Laser

48. The resolving power of a telescope depends on

The ratio of the focal length and the diameter

Its diameter (of the objective)

Its focal length

Its magnification

49. 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

50 m

10 m

1 m

5 m

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

All of these

At the focus

Inside the focus

Between f and 2f

Page 3 of 6

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

d sin θ = (m + 1)²

d sin θ = (m + 1/2)

d sin θ = (m + 1/2)²

d sin θ = (m + 1/2)⁴

52. 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

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

Gets halved

Remains unchanged

Increases

Decreases

54. In a compound microscope, the intermediate image is

Virtual, erect and magnified

Virtual, inverted and magnified

Real, erect and magnified

Virtual, erect and reduced

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

Five times shorter than that of eye piece

Equal to that of the eye piece

Greater than that of eye piece

Shorter than that of eye piece

56. Choose the correct statement

Rays may be normal to wave front

Rays are not normal to wave front

There is no relationship between rays and wave fronts

Rays are normal to wave front

57. 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 air

Water to glass

58. A polarizer is used to

Produce polarized light

Produce unpolarised light

Increase intensity of light

Reduced intensity of light

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

Green

Red

Orange

Violet

60. For constructive interference the path difference is

m²λ

mλ

½ mλ

(m – 1) λ

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

0 and 25 cm

0 and infinity

25 cm and infinity

25 cm and 100 cm

62. 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

Larger

Infinite

None of these

Smaller

63. What is the most important function of telescope?

None of these

Resolution

Light collection

Magnification

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

Laser rays are high velocity waves

Laser rays are not absorbed

Laser rays are most coherent waves

Laser rays propagate in a straight line

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

4.5 x 10⁸ cm

5.5 x 10⁵

6.5 x 10⁸

2 x 10⁵ ms¯¹

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

The diameter of the objective

The focal length of the objective

Two of the above

The focal length of eyepiece

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

Line spectrum

All of these

Emission spectrum

Continuous emission spectrum

68. 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

Energy of different colors is different

Velocity of different colors is different

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

25l

16l

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

Interference

Diffraction

Refraction

Reflection

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

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

(m + 1/2)λ

mλ

½ mλ

(m – 1/2)λ

73. Optic fibers are related with

Light

None of these

Communication

Computer

74. 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

Halved

Quadrupled

Unchanged

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

Line spectrum

All of these

Emission spectrum

Continuous emission spectrum

Page 4 of 6

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

Line spectrum

Continuous spectrum

Band spectrum

Discontinuous spectrum

77. 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°

78. 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 have extremely low transmission loss

Optical fibers are subject to electromagnetic interference from outside

Optical fibers can be of graded refractive index

79. In 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

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

81. 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 10¹¹ to 5 x 10¹⁴ Hz

5 x 10⁸ to 5 x 10¹¹ Hz

5 x 10¹⁴ to 5 x 10¹⁷ Hz

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

Electromagnetic

Monochromatic

In the form of a narrow beam

Incoherent

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

Source

Origin

Base

Producer

84. There is no noticeable boundary between core and cladding

Single mode step index fiber

All types of fiber

Multi-mode graded index fiber

Multi-mode step index fiber

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

260

240

280

200

86. The fringe spacing in case of blue light

Remains the same

None of these

Decrease

Increases

87. In a compound microscope, the intermediate image is

Virtual, erect and magnified

Real, erect and magnified

Virtual, erect and reduced

Virtual, inverted and magnified

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

Convex

Plane

Concave

None

89. The cause of mirage observed in desert is

Refraction

Total internal reflection

Reflection

Scattering

90. In a simple microscope lens used is _________.

Plano convex

Biconvex

Biconcave

Cylindrical

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 = 2π dm

λ = 2d/m

λ = dm

2λ = dm

92. 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

93. 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

Interference pattern produced due to thin oil film

Total internal reflection of light

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

Dispersion

Refraction

Scattering

Reflection

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

Different wavelength

Of nearly the same frequency

Of same frequency

Of the same frequency and having definite phase relationship

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

Pole of the lens

Principal focus of the lens

Aperture of the lens

Radius of curvature of the lens

97. 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?

10 cm

15 cm

20 cm

25 cm

98. 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

Single mode step index fiber

Multi-mode step index fiber

99. Which does not show polarization?

Transverse wave in gas

Both A and B

Longitudinal waves in gas

None of these

100. 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

Increasing gradually

Decreasing gradually

Page 5 of 6

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

Convex

Concave

Plane

None

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

Optical center

Focus

Center of curvature

Aperture

103. The setting of Newton’s rings is

A Plano convex lens and the plane glass plate

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

None of these

A Plano convex lens and simple glass sheet

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

0.2

0.5

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

3 meters

2 meters

1 meter

4 meters

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

Of difference frequencies

White light

Added

Coherent

107. 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

108. Inverse square law for luminance is valid for

Cylindrical source

Isotropic point source

Search light

All types of sources

109. 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 m²

R = N x m

110. 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 cm

3 cm

3.5 cm

2.5 cm

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

Band absorption spectrum

Band emission spectrum

Line emission spectrum

Line absorption spectrum

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

Neither zero (0) nor one (1)

Zero (0)

One (1)

Both zero (0) and one (1)

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

Double-convex

Plano-concave

Plano-convex

Convexo-concave

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

Total internal reflection

Refraction

Dispersion of light

Reflection

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

Doppler’s effect

Diffraction

Interference

None of these

116. The resolving power of telescope depends on

Length of the telescope

Diameter of the objective lens

Focal length of objective lens

Focal length of eye lens

117. Magnifying power of simple microscope

No effect with decrease or increase with focal length

List distance of distinct vision

Increase with increase in focal length

Increase with decrease in focal length

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

Diffraction

Refraction

Origin of spectra

Reflection

119. Inverse square law for luminance is valid for

Isotropic point source

All types of sources

Search light

Cylindrical source

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

Speed of propagation of the wave

None of these

Speed of propagation less than the wave

Speed of propagation greater than wave

121. The diameter of a lens is called

Principal axis

Radius of curvature

Focal length

Aperture

122. 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 Erect

Real and inverted

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

Deviation angle

Refractive angle

Critical angle

Incidence angle

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

1/9 times

1/3 times

3 times

9 times

125. Wavelength of light of frequency 100 Hz is

2 x 10⁶ m

4 x 10⁶ m

3 x 10⁶ m

5 x 10⁶ m

Page 6 of 6

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

The focus of the objective lens

Infinity

The least distance of the distinct vision

The focal of the eye piece

127. Geometrical optics cannot give following characteristics for a microscope

Any of the above

Image size

Image position

Resolution of image

128. Which part of the spectrum is most visible?

Violet

Yellow-green

Yellow

Red

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

Converging (or convex) lens

Plano convex lens

Diverging (or concave) lens

Plano concave lens

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

Wave front

Vibrator

A half-period zone

A ray

131. Which is having minimum wavelength?

Ultra-violet rays

X-rays

ϒ-rays

Cosmic-rays

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

Virtual and erect

Real and erect

Virtual

Real and inverted

133. Choose the correct statement

Raya may be normal to wave front

Rays are normal to wave front

There is no relationship between rays and wave fronts

Rays are not normal to wave front

134. 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

135. Geometrical optics cannot give following characteristics for a microscope

Image size

Image position

Any of the above

Resolution of image

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: 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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ECAT Physics Optics Chapter Online Test

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