physics MCQs - 11th class Chapter 09 Mcqs

1

Who proposed that light energy travels in space as waves in 1678?

A

Isaac Newton

B

Thomas Young

C

Christian Huygen

D

Albert Michelson

2

A surface on which all points have the same phase of vibration is known as a?

A

Wavelet

B

Wavefront

C

Ray of light

D

Light beam

3

For a distant point source like the Sun, the wavefronts reaching the Earth are considered to be?

A

Spherical

B

Cylindrical

C

Plane

D

Irregular

4

According to Huygen's principle, every point on a wavefront acts as a source of?

A

Primary wavelets

B

Secondary wavelets

C

Tertiary wavelets

D

Stationary waves

5

Which of the following is a necessary condition for observable interference of light?

A

The sources must be of different wavelengths

B

The sources must be incoherent

C

The sources must be monochromatic and coherent

D

The light must be polarized

6

In Young's double-slit experiment, the central fringe is always?

A

Dark

B

Bright

C

Coloured

D

Of zero intensity

7

The phenomenon of interference of light provides experimental evidence for the?

A

Particle nature of light

B

Wave theory of light

C

Quantum theory of light

D

Electromagnetic nature of light

8

For constructive interference in Young's experiment, the path difference must be?

A

An odd multiple of half-wavelength

B

An integral multiple of wavelength

C

A fractional multiple of wavelength

D

Zero only

9

The equation for the position of the m-th bright fringe from the central point is y = ?

A

mλd/L

B

(m+1/2)λL/d

C

mλL/d

D

λL/d

10

If the distance between the slits in Young's experiment is decreased, the fringe spacing will?

A

Decrease

B

Increase

C

Remain the same

D

Become zero

11

The beautiful colours seen in a thin oil film on water are due to?

A

Diffraction

B

Dispersion

C

Polarization

D

Interference

12

In the setup for Newton's rings, the central spot is dark due to?

A

Constructive interference

B

An additional path difference of λ/2 on reflection

C

The lens and plate being in perfect contact

D

Diffraction effects

13

Michelson's interferometer is an instrument used to measure?

A

Wavelength with high precision

B

Frequency of light

C

Speed of light

D

Intensity of light

14

In a Michelson's interferometer, if the movable mirror is displaced by a distance L, and m fringes shift, the relationship is?

A

L = mλ

B

L = mλ/2

C

L = 2mλ

D

L = m/λ

15

The property of bending of light around obstacles is called?

A

Interference

B

Refraction

C

Polarization

D

Diffraction

16

Diffraction effects are most prominent when the size of the obstacle is?

A

Much larger than the wavelength of light

B

Much smaller than the wavelength of light

C

Comparable to the wavelength of light

D

Equal to the amplitude of light

17

For a single slit of width d, the condition for the first minimum in the diffraction pattern is d sinθ = ?

A

λ/2

B

λ

C

3λ/2

D

2λ

18

A glass plate with a large number of close, parallel, equidistant slits ruled on it is called a?

A

Polaroid

B

Prism

C

Diffraction grating

D

Michelson interferometer

19

In a diffraction grating, the zero-order maximum is formed in which direction?

A

At 90 degrees to the normal

B

Along the direction of the normal (θ=0)

C

At 45 degrees to the normal

D

It does not exist

20

The equation for the n-th order maximum for a diffraction grating is?

A

d sinθ = (n+1/2)λ

B

2d sinθ = nλ

C

d = nλ sinθ

D

d sinθ = nλ

21

Which phenomenon is used to study the atomic structure of crystals?

A

Interference

B

X-ray diffraction

C

Polarization

D

Refraction

22

Bragg's equation for X-ray diffraction is given by?

A

d sinθ = nλ

B

2d sinθ = nλ

C

d sinθ = 2nλ

D

2d = nλ sinθ

23

Polarization of light proves that light waves are?

A

Longitudinal

B

Stationary

C

Transverse

D

Mechanical

24

A material that transmits light with vibrations in only one plane is called a?

A

Diffuser

B

Grating

C

Polaroid

D

Lens

25

When unpolarized light passes through a Polaroid, the intensity of the transmitted light is?

A

Doubled

B

Halved

C

Unchanged

D

Zero

26

Optically active substances, like a sugar solution, have the ability to?

A

Rotate the plane of polarization

B

Increase the speed of light

C

Change the wavelength of light

D

Reflect light completely

27

The distance between two consecutive wavefronts is equal to one?

A

Frequency

B

Amplitude

C

Wavelength

D

Period

28

Two sources of light are coherent if they emit waves of the same wavelength and maintain a?

A

Variable phase difference

B

Constant phase difference

C

Zero amplitude

D

Random polarization

29

In Young's experiment, dark fringes are also known as?

A

Maxima

B

Minima

C

Primary fringes

D

Secondary fringes

30

For a dark fringe to appear at a point P in Young's experiment, the path difference BD must be?

A

mλ

B

(m+1/2)λ

C

2mλ

D

mλ/2

31

The fringe spacing (Δy) in Young's experiment is directly proportional to the?

A

Slit separation d

B

Order of the fringe m

C

Wavelength λ

D

Frequency f

32

If white light is used in Young's double-slit experiment, the central fringe will be?

A

White

B

Black

C

Red

D

Violet

33

Newton's rings are formed due to interference in a thin film of?

A

Water

B

Oil

C

Glass

D

Air

34

Michelson showed that the standard metre was equivalent to 1,553,163.5 wavelengths of which light?

A

Yellow sodium light

B

Blue mercury light

C

Red cadmium light

D

Green argon light

35

In a single-slit diffraction pattern, the central bright region is?

A

The same width as other bright regions

B

Narrower than other bright regions

C

Wider than other bright regions

D

Completely dark

36

The quantity 'd' in the diffraction grating formula d sinθ = nλ is called the?

A

Slit width

B

Grating constant

C

Grating element

D

Wavelength

37

If a diffraction grating has N lines over a length L, the grating element d is given by?

A

N/L

B

L/N

C

L × N

D

L + N

38

Higher-order spectra produced by a diffraction grating are?

A

More separated

B

Less separated

C

Equally spaced as the first order

D

Brighter than the zero order

39

X-rays are suitable for studying crystal structure because their wavelength is of the order of?

A

10^-3 m

B

10^-7 m

C

10^-10 m

D

10^-12 m

40

In the Bragg equation 2d sinθ = nλ, 'd' represents the?

A

Diameter of an atom

B

Thickness of the crystal

C

Distance between crystal planes

D

Wavelength of X-ray

41

The phenomenon of polarization is associated with what type of waves?

A

Sound waves

B

Longitudinal waves

C

Water waves

D

Transverse waves

42

If two Polaroids are placed with their axes perpendicular to each other (crossed), the transmitted light intensity will be?

A

Maximum

B

Half

C

Minimum (ideally zero)

D

Unchanged

43

Glare from a road surface is significantly reduced by Polaroid sunglasses because the reflected light is?

A

Unpolarized

B

Completely polarized

C

Partially polarized

D

Circularly polarized

44

The path difference between two rays interfering constructively must be an integer multiple of?

A

λ/4

B

λ/2

C

λ

D

2λ

45

The path difference between two rays interfering destructively must be an odd integer multiple of?

A

λ/4

B

λ/2

C

λ

D

2λ

46

In Michelson's interferometer, a 'compensator plate' G2 is used to?

A

Increase the wavelength

B

Equalize the path length in glass for both beams

C

Polarize the light

D

Focus the beams

47

What happens to the fringe spacing in Young's experiment if the entire apparatus is immersed in water?

A

Increases

B

Decreases

C

Remains unchanged

D

Fringes disappear

48

The study of light as a wave phenomenon is called?

A

Geometrical Optics

B

Quantum Optics

C

Physical Optics

D

Ray Optics

49

In the equation for a dark fringe, y = (m + 1/2)Lλ/d, the first dark fringe corresponds to m = ?

A

1

B

1/2

C

0

D

-1