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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. Which does not show polarization?

Transverse wave in gas

Longitudinal waves in gas

Both A and B

None of these

2. 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

Decreasing the distance between the screen and the slits

Using monochromatic light of longer wavelength

Using monochromatic light of higher frequency

3. 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

9 times

3 times

4. 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

Shorter than that of eye piece

Greater than that of eye piece

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

25l

16l

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

260

280

200

240

7. 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

Water to glass

Glass to air

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

R = N x m

R = N x m²

R = N/m

R = m/N

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

Diffraction

Dispersion

Refraction

Reflection

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

White light

Coherent

Added

Of difference frequencies

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

None of these

Frequency

Wavelength

Amplitude

12. The diameter of a lens is called

Focal length

Aperture

Radius of curvature

Principal axis

13. 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

6 cm

1.9 cm

4.8 cm

14. 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°

100°

50°

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

(m – 1/2)λ

(m + 1/2)λ

mλ

½ mλ

16. Resolving power of a telescope depends on:

Refractive index of objective lens

Diameter of objective lens

The focal length of objective lens

The magnification of eyepiece

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

Interference

Diffraction

Reflection

Refraction

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

.m Sin θ = (d + ½)λ

½ d Sin θ = mλ

2π Sin θ = (m + ½)λ

.d Sin θ = (m + ½)λ

19. 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

2 cm

2.5 cm

3 cm

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

Laser rays are not absorbed

Laser rays are high velocity waves

Laser rays are most coherent waves

Laser rays propagate in a straight line

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

Speed of propagation less than the wave

Speed of propagation greater than wave

Speed of propagation of the wave

None of these

22. 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

23. The resolving power of a telescope depends on

Its focal length

The ratio of the focal length and the diameter

Its diameter (of the objective)

Its magnification

24. Geometrical optics cannot give following characteristics for a microscope

Resolution of image

Image position

Any of the above

Image size

25. There is no noticeable boundary between core and cladding

Single mode step index fiber

Multi-mode step index fiber

All types of fiber

Multi-mode graded index fiber

Page 2 of 6

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

Diffraction

Refraction

Reflection

Origin of spectra

27. Inverse square law for luminance is valid for

Cylindrical source

Isotropic point source

Search light

All types of sources

28. The fringe spacing in case of blue light

Remains the same

None of these

Decrease

Increases

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

Continuous emission spectrum

Line spectrum

All of these

Emission spectrum

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

Total internal reflection

Reflection

Refraction

Dispersion of light

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

At the focus

Between f and 2 f

Beyond 2f

At 2f

32. In a compound microscope, the intermediate image is

Virtual, inverted and magnified

Virtual, erect and reduced

Virtual, erect and magnified

Real, erect and magnified

33. 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

Quadrupled

Doubled

Halved

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

None

Concave

Convex

Plane

35. 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

Housefly will be seen enlarged in image

Intensity of image will be increased

Housefly will be seen reduced in image

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

37. 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 water

Glass to air

Water to air

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

Two of the above

The focal length of the objective

The diameter of the objective

The focal length of eyepiece

39. What is the most important function of telescope?

Light collection

Magnification

None of these

Resolution

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

Interference

Reflection

Diffraction

Refraction

41. Soap bubble looks colored due to

Interference

Dispersion

Reflection

Any one of these

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

Green

Orange

Red

Violet

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

Line spectrum

Continuous spectrum

Band spectrum

Discontinuous spectrum

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

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

Velocity of different colors is different

Energy of different colors is different

Amplitude of different colors is different

Phase of different colors is different

46. 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

25 cm

15 cm

20 cm

47. In a 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

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

½ times

2 times

¼ times

4 times

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

Decreasing gradually

Increasing gradually

None of these

It is constant at the center

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

Ultrasonics

Light

Sound

Supersonics

Page 3 of 6

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

Parabolic

Circular

Straight

Elliptical

52. The revolving power of a lens is given by

αmin = 1.28 D/λ

αmin = 1.21 λ/D

αmin = 1.22 D/λ

αmin = 1.22 λ/D

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

Base

Producer

Source

Origin

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

0 and 25 cm

25 cm and 100 cm

25 cm and infinity

0 and infinity

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

Line absorption spectrum

Band emission spectrum

Line emission spectrum

Band absorption spectrum

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

Y = (m+1/2)λd/L

Y = (m+1/2) dL/λ

Y = (m+1)λL/d

Y = (m+1/2)λL/d

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

The focal of the eye piece

Infinity

The focus of the objective lens

The least distance of the distinct vision

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

Electromagnetic

In the form of a narrow beam

Incoherent

Monochromatic

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

60. For constructive interference the path difference is

(m – 1) λ

m²λ

½ mλ

mλ

61. For the normal setting of a telescope

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

Only the final image is at infinity

Only the object is at infinity

Both the object and the final image is at infinity

62. 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

Beyond 2 f

At the principal focus

63. The cause of mirage observed in desert is

Refraction

Total internal reflection

Reflection

Scattering

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

Zero

Different

Different with refractive index of core higher than cladding

Same

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

None of these

Minimum

Maximum

Zero

66. 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)

d sin θ = (m + 1/2)²

67. 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

2 x 10⁵ ms¯¹

6.5 x 10⁸

68. 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

5 m

10 m

1 m

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

Real and Erect

Virtual and Erect

Virtual and inverted

Real and inverted

70. 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 can be of graded refractive index

Optical fibers have extremely low transmission loss

71. 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

72. 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

73. 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 10¹⁴ to 5 x 10¹⁷ Hz

5 x 10¹¹ to 5 x 10¹⁴ Hz

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

Distance between the slits

Fringe width

Wavelength

Intensity ratio of the sources

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

Refraction

Scattering

Reflection

Dispersion

Page 4 of 6

76. Inverse square law for luminance is valid for

All types of sources

Search light

Isotropic point source

Cylindrical source

77. Unit of power of a lens is

Meter

Horsepower

Diopter

Watt

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

None of these

fₑ + fₒ

fₒ - fₑ

fₑ - fₒ

79. 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

80. Wavelength of light of frequency 100 Hz is

2 x 10⁶ m

5 x 10⁶ m

3 x 10⁶ m

4 x 10⁶ m

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

A half-period zone

Vibrator

A ray

Wave front

82. A polarizer is used to

Reduced intensity of light

Produce unpolarised light

Produce polarized light

Increase intensity of light

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

All of these

Continuous emission spectrum

Line spectrum

Emission spectrum

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

Inside the focus

Between f and 2f

All of these

At the focus

85. 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

Smaller

None of these

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

0.2

0.5

87. 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

2λ = dm

λ = 2π dm

λ = dm

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

Repeaters

Laser

Transformer

Diodes

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

Perpendicular

Equal

Parallel

Opposite

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

None of these

Different width

Equal width

Dark fringes are thicker than bright

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

Of same frequency

Of nearly the same frequency

Of the same frequency and having definite phase relationship

Different wavelength

92. Optic fibers are related with

Light

Communication

Computer

None of these

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

Energy

Intensity

Momentum

Amplitude

94. 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 virtual

Image is formed at + ∞ and is real

Image is formed at - ∞ and is real

95. The setting of Newton’s rings is

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

A Plano convex lens and simple glass sheet

None of these

A Plano convex lens and the plane glass plate

96. The power of a concave lens is

Positive

Negative

Real

Virtual

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

Do not affect a photographic plate

Have a lower frequency

Cannot be diffracted

Cannot be polarized

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

Infrared

Sun light

Sodium light

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

Plane

Convex

Concave

None

100. The cause of mirage observed in desert is

Total internal reflection

Reflection

Scattering

Refraction

Page 5 of 6

101. The resolving power of telescope depends on

Focal length of eye lens

Length of the telescope

Focal length of objective lens

Diameter of the objective lens

102. Final image produced by a compound microscope is

Real and inverted

Virtual and erect

Real and erect

Virtual and inverted

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

Double-convex

Convexo-concave

Plano-concave

Plano-convex

104. Which part of the spectrum is most visible?

Violet

Yellow-green

Yellow

Red

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

All of the above

Chromatic aberration as well as spherical aberration

Chromatic aberration

Spherical aberration

106. 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

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

Principal focus of the lens

Aperture of the lens

Radius of curvature of the lens

Pole of the lens

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

All of these

Collimator

Turn table

Telescope

109. Which is having minimum wavelength?

X-rays

Cosmic-rays

Ultra-violet rays

ϒ-rays

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

One (1)

Neither zero (0) nor one (1)

Both zero (0) and one (1)

Zero (0)

111. 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

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

Incoherent

Monochromatic

In the form of a narrow beam

Electromagnetic

113. In a compound microscope, the intermediate image is

Virtual, erect and magnified

Virtual, erect and reduced

Virtual, inverted and magnified

Real, erect and magnified

114. Choose the correct statement

Rays are normal to wave front

There is no relationship between rays and wave fronts

Rays are not normal to wave front

Rays may be normal to wave front

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

Plano convex lens

Diverging (or concave) lens

Plano concave lens

Converging (or convex) lens

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

Incidence angle

Critical angle

Refractive angle

Deviation angle

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

Monochromatic

Of high intensity

Coming from opposite direction

Of two different frequencies

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

λD/d

λD/4d

2λD/d

λD/2d

119. Magnifying power of simple microscope

Increase with increase in focal length

No effect with decrease or increase with focal length

List distance of distinct vision

Increase with decrease in focal length

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

3 meters

2 meters

1 meter

4 meters

121. In a simple microscope lens used is _________.

Cylindrical

Biconvex

Plano convex

Biconcave

122. Wavelength of light of frequency 100 Hz is

5 x 10⁶ m

4 x 10⁶ m

3 x 10⁶ m

2 x 10⁶ m

123. 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

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

Red

Green

Yellow

Blue

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

11 diopter

10 diopter

2/10 diopter

1/10 diopter

Page 6 of 6

126. Ray optics is valid, when characteristic dimensions are

Of the same order as the wavelength of light

Of the order of one millimeter

Much smaller than the wavelength of length

Much larger than the wavelength of light

127. 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

Aperture

Focus

128. Resolving power of a telescope depends on:

The focal length of objective lens

Diameter of objective lens

Refractive index of objective lens

The magnification of eyepiece

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

Amplitude

Frequency

Wavelength

Velocity

130. Magnification of the astronomical telescope is

fo+fe

fe/fo

(1+fo/fe)L/fo

fo/fe

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

Virtual

Virtual and erect

Real and inverted

Real and erect

132. Which of the following has least wavelength?

Ultra-violet rays

Cosmic-rays

ϒ-rays

X-rays

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

Multi-mode graded index fiber

Multi-mode step index fiber

Single mode step index fiber

Mono mode step index fiber

134. Geometrical optics cannot give following characteristics for a microscope

Any of the above

Image position

Image size

Resolution of image

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

Increases

Decreases

Gets halved

Remains unchanged

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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ECAT Physics Optics Chapter Online Test

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