Physics Lights and Optics Online Mcqs Test

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Question 1

1. Interference was observed in interference chamber, when air was present, now the chamber is evacuated and if the same light is used, a careful observer will see

Answer

Interference with dark bands

Answer

No interference

Answer

Interference in which breadth of the fringe will be slightly increase

Answer

Interference with bright bands

Question 2

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

Answer

Speed of propagation less than the wave

Answer

Speed of propagation greater than wave

Answer

Speed of propagation of the wave

Question 3

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

Answer

Fringe width

Answer

Wavelength

Answer

Distance between the slits

Answer

Intensity ratio of the sources

Question 4

4. Appearance of colour in thin films is due to

Answer

Dispersion

Answer

Interference

Answer

Polarization

Answer

Diffraction

Question 5

5. The cause of mirage observed in desert is

Answer

Refraction

Answer

Reflection

Answer

Scattering

Answer

Total internal reflection

Question 6

6. Polarization occurs only in ________ waves

Answer

Longitudinal

Answer

Mechanical waves

Answer

Matter waves

Answer

Transverse

Question 7

7. The condition for constructive interference of two coherent beams is that the path difference should be

Answer

Odd integral multiple of λ/2

Answer

Integral multiple of λ/2

Answer

Even integral multiple of λ

Answer

Integral multiple of λ

Question 8

8. Huygen’s wave theory of light cannot explain

Answer

Interference

Answer

Photoelectric effect

Answer

Polarization

Answer

Diffraction

Question 9

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

Answer

Reflection

Answer

Diffraction

Answer

Origin of spectra

Answer

Refraction

Question 10

10. Two sources of light are coherent if they emit rays of

Answer

Same amplitude of vibration

Answer

Same wave length with constant phase difference

Answer

Same amplitude and wavelength

Answer

Same wavelength

Question 11

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

Answer

Reflection

Answer

Diffraction

Answer

Refraction

Answer

Origin of spectra

Question 12

12. The idea of light as wave produced by

Answer

Thomos young

Question 13

13. The fringe spacing in case of blue light

Answer

Remains the same

Answer

None of these

Question 14

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

Answer

Wave front

Answer

A half-period zone

Question 15

15. One condition for interference is that the two sources should be coherent and:

Answer

At a far off distance

Answer

Opposite to each other

Answer

Coinciding

Answer

Close together

Question 16

16. When the light is incident on polarizing angle which of the following is completely polarized?

Answer

Refracted light

Answer

Neither reflected nor refracted light

Answer

Reflected light

Answer

Both reflected and refracted light

Question 17

17. When crest of one wave falls over the trough of the other wave this phenomenon is known as

Answer

Destructive interference

Answer

Diffraction

Answer

Polarization

Answer

Constructive interference

Question 18

18. Which of the following has least wavelength?

Answer

Ultra-violet rays

Answer

Cosmic-rays

Question 19

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

Answer

Phase of different colors is different

Answer

Energy of different colors is different

Answer

Velocity of different colors is different

Answer

Amplitude of different colors is different

Question 20

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

Answer

Cannot be polarized

Answer

Have a lower frequency

Answer

Cannot be diffracted

Answer

Do not affect a photographic plate

Question 21

21. The setting of Newton’s rings is

Answer

None of these

Answer

A Plano convex lens and simple glass sheet

Answer

A Plano convex lens and the plane glass plate

Answer

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

Question 22

22. In Michelson interferometer to switch the fringe from bright to dark the mirror should be displaced through

Question 23

23. The condition for the bright fringes formed due to constructive interference in a diffraction grating is:

Answer

d sin θ = mλ

Answer

d sin θ = m/2 λ

Answer

d sin θ = 2λm

Answer

md cos θ = λ

Question 24

24. Diffraction effect is

Answer

More for a sharp edge

Answer

Less for a round edge

Answer

More for a round edge

Answer

Less for a sharp edge

Question 25

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

Question 26

26. The locus of all points in the same phase of vibration is called:

Answer

Wave number

Answer

Wavelength

Answer

Wave front

Question 27

27. Light on passing through a Polaroid is

Answer

Elliptically polarized

Answer

Un-polarized

Answer

Circularly polarized

Answer

Plane polarized

Question 28

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

Answer

It is constant at the center

Answer

None of these

Answer

Increasing gradually

Answer

Decreasing gradually

Question 29

29. The locus of all points in a medium having the same phase of vibration is called

Answer

Wavelength

Answer

Wave front

Question 30

30. According to the electromagnetic theory, the speed of light is approximately:

Answer

3 x 10⁸ ms¯¹

Answer

3 x 10¯¹⁰ ms¯¹

Answer

3.1 x 10⁸ ms¯¹

Answer

3 x 10⁵ ms¯¹

Question 31

31. For the sustained interference of light, the necessary condition is that the two sources should

Answer

Of same amplitude

Answer

Have constant phase difference

Answer

Be close to each other

Question 32

32. A thin film is a transparent medium whose thickness with the wavelength of light are

Answer

None of these

Answer

Not comparable

Answer

Comparable

Question 33

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

Answer

Emission spectrum

Answer

Line spectrum

Answer

Continuous emission spectrum

Answer

All of these

Question 34

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

Answer

Monochromatic

Answer

Incoherent

Answer

In the form of a narrow beam

Answer

Electromagnetic

Question 35

35. For constructive interference the path difference is

Answer

(m – 1)λ

Question 36

36. Crystals of a material can behave as

Answer

Interferometer

Answer

Convex lens

Answer

Diffraction grating

Question 37

37. Longitudinal waves do not exhibit

Answer

Polarization

Answer

Diffraction

Answer

Reflection

Answer

Refraction

Question 38

38. Diffraction fringes are

Answer

Distance between them increases

Answer

They are adjacent with no space in between

Answer

Distance between then decreases

Answer

Equally spaced

Question 39

39. Light is a type of energy which produces sensation of

Answer

None of these

Question 40

40. Which of the following properties show light is transverse wave in nature?

Answer

Polarization

Answer

Interference

Answer

Reflection

Answer

Diffraction

Question 41

41. Ray optics is valid, when characteristic dimensions are

Answer

Much smaller than the wavelength of length

Answer

Much larger than the wavelength of light

Answer

Of the same order as the wavelength of light

Answer

Of the order of one millimeter

Question 42

42. Central spot of New tons rings

Answer

Dart for large wavelength

Answer

Bright for large wavelength

Question 43

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

Answer

Line absorption spectrum

Answer

Band emission spectrum

Answer

Line emission spectrum

Answer

Band absorption spectrum

Question 44

44. A polarizer is used to

Answer

Produce polarized light

Answer

Reduced intensity of light

Answer

Increase intensity of light

Answer

Produce unpolarised light

Question 45

45. Can two head lights of car can produce interference

Answer

Partly produce interference

Answer

None of these

Question 46

46. Choose the correct statement

Answer

Rays are normal to wave front

Answer

Rays are not normal to wave front

Answer

Rays may be normal to wave front

Answer

There is no relationship between rays and wave fronts

Question 47

47. In Young double slit experiment, if white light is used

Answer

Colored fringes will be seen

Answer

No interference fringes will be seen

Answer

Impossible to predict

Answer

Alternate dark and bright fringes will be seen

Question 48

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

Answer

d in θ = (m + ½ )1/λ

Answer

d sin θ = (m + 1/2)π/λ

Answer

d sin θ = (m + 1)λ

Answer

d sin θ = (m + 1/2)λ

Question 49

49. Light appears to travel in straight lies since

Answer

It is not absorbed by the atmosphere

Answer

It is reflected by the atmosphere

Answer

Its wavelength is very small

Answer

Its velocity is very large

Question 50

50. A point source of light placed in a homogeneous medium gives rise to

Answer

An elliptical wave front

Answer

A spherical wave front

Answer

A plane wave front

Answer

A cylindrical wave front

Question 51

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

Answer

In the form of a narrow beam

Answer

Electromagnetic

Answer

Incoherent

Answer

Monochromatic

Question 52

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

Answer

Doppler’s effect

Answer

Diffraction

Answer

Interference

Answer

None of these

Question 53

53. Wavelength of light of frequency 100 Hz is

Answer

3 x 10⁶ m

Answer

2 x 10⁶ m

Answer

4 x 10⁶ m

Answer

5 x 10⁶ m

Question 54

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

Answer

Y = (m + ½) dL/λ

Answer

Y = (m + 1) λL/d

Answer

Y = (m + 1/2) λd/L

Answer

Y = (m + 1/2) λL/d

Question 55

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

Answer

Elliptical

Question 56

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

Answer

d Sin θ = (m + 1/2)λ

Answer

m Sin θ = (d + 1/2)λ

Answer

2π Sin θ = (m + 1/2)λ

Answer

½ d Sin θ = mλ

Question 57

57. A diffraction grating has 500 lines per mm. Its slit spacing or grating element will be equal to

Answer

2 x 10¯³ mm

Answer

5 x 10¯³ mm

Answer

2 x 10¯⁵ mm

Question 58

58. A ____________ lens is used to form Newton’s rings.

Answer

Plano-concave

Answer

Double-convex

Answer

Plano-convex

Answer

Convexo-concave

Question 59

59. The blue colour of the sky is due to

Answer

Reflection

Answer

Diffraction

Answer

Polarization

Answer

Scattering

Question 60

60. 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?

Answer

Increasing the distance between the slits

Answer

Using monochromatic light of longer wavelength

Answer

Using monochromatic light of higher frequency

Answer

Decreasing the distance between the screen and the slits

Question 61

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

Question 62

62. Wave front is the locus of all points in vibration are in the same

Answer

All of these

Answer

Wavelength

Question 63

63. In Newton’s rings the point of contact of the lend and the glass plate, the air film is

Answer

None of these

Question 64

64. In a plane polarized light

Answer

Vibration in all direction

Answer

Vibration in two mutually perpendicular directions

Answer

Vibration take place in a direction perpendicular to the direction of propagation of light

Answer

No vibration at all

Answer 210

Equal width

Answer 211

None of these

Answer 212

Different width

Answer 213

Dark fringes are thicker than bright

Answer 214

5 x 10⁵ to 5 x 10¹¹ Hz

Answer 215

5 x 10⁵ to 5 x 10⁵ Hz

Answer 216

5 x 10¹¹ to 5 x 10¹⁴ Hz

Answer 217

5 x 10¹⁴ to 5 x 10¹⁷ Hz

Answer 218

None of these

Answer 219

Source of wave front

Answer 220

Source of secondary wave front

Answer 221

Light can be diffracted

Answer 222

The intensity of light from a point source falls off inversely as the square of the distance from the source

Answer 223

Light can be polarized

Answer 224

Two coherent light waves can be made to interfere

Answer 225

None of these

Answer 226

A point source

Answer 227

A extended source

Answer 228

λ = 2π dm

Answer 229

Refraction

Answer 230

Diffraction

Answer 231

Reflection

Answer 232

Transmission

Answer 233

Interference pattern produced due to thin oil film

Answer 234

Total internal reflection of light

Answer 235

Polarization

Answer 236

Diffraction pattern

Answer 237

Refraction

Answer 238

Diffraction

Answer 239

Reflection

Answer 240

Interference

Answer 241

Radio waves

Answer 242

Sound waves

Answer 243

Ultraviolet rays

Answer 244

Diffraction

Answer 245

Photoelectric effect

Answer 246

Polarization

Answer 247

Interference

Answer 248

Reflection

Answer 249

Refraction

Answer 250

Interference

Answer 251

Dispersion

Answer 252

Dark fringes are wider than bright fringe

Answer 253

Central fringes are brighter than the outer fringes

Answer 254

Both dark and bright fringes are of equal width

Answer 255

Bright fringes are wider than dark fringes

Answer 256

Light can be diffracted

Answer 257

Light can be polarized

Answer 258

The intensity of light from a point source falls off inversely as the square of the distance from the source

Answer 259

Two coherent light waves can be made to interfere

Answer 260

Laser rays propagate in a straight line

Answer 261

Laser rays are most coherent waves

Answer 262

Laser rays are high velocity waves

Answer 263

Laser rays are not absorbed

Answer 264

A longitudinal wave

Answer 265

A transverse waves

Answer 266

A sound wave

Answer 267

An electromagnetic wave

Answer 268

Supersonics

Answer 269

Ultrasonics

Answer 270

Reflection of light

Answer 271

Diffraction of light

Answer 272

Interference of light

Answer 273

None of these

Answer 274

Polarization

Answer 275

Absorption

Answer 276

Transmission

Answer 277

Diffraction

Answer 278

None of these

Answer 279

Bragg’s law

Answer 280

Huygen’s formula

Answer 281

Laue’s pattern

Answer 282

Compton effect

Answer 283

Interference pattern produced due to thin oil film

Answer 284

Diffraction pattern

Answer 285

Polarization

Answer 286

Total internal reflection of light

Answer 287

Of same frequency

Answer 288

Of nearly the same frequency

Answer 289

Different wavelength

Answer 290

Of the same frequency and having definite phase relationship

Total Questions:	88
Time Allowed:	40 Minutes
Total Marks:	88
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Physics Lights and Optics Online Mcqs Test

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Important Lights and Optics Question and Answer

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