Question 1

A wave that travels from a medium of lower index of refraction to a medium of higher index of refraction undergoes 180° phase changes relative to the incident wave.

Accepted Answer

When a wave travels from a medium of lower refractive index to a medium of higher refractive index, it undergoes a phase change of 180° relative to the incident wave. This phenomenon is called reflection.

Question 2

In Young's double-slit experiment, light coming from each slit arrives in phase at the first maximum on either side of the central bright fringe.

Accepted Answer

This is known as the first-order maximum or first-order fringe, and occurs when the path difference between the two waves is equal to one wavelength. At this point, the waves are in phase and constructively interfere to create a bright fringe.

Question 3

The particle theory of light, as well as the wave theory of light, are both supported by the interference of light.

Accepted Answer

The interference of light is a phenomenon that supports both the particle theory and the wave theory of light. Interference patterns can be observed when light waves interact with each other, which is explained by the wave theory. At the same time, the photoelectric effect, which is explained by the particle theory, also provides evidence for the existence of photons, which are particles of light. Therefore, both theories are supported by the interference of light.

Question 4

When light travels from a larger index of refraction towards a smaller index of refraction, there is no phase change upon reflection at the boundary.

Accepted Answer

When light travels from a larger index of refraction towards a smaller index of refraction, there will be a phase change upon reflection at the boundary. However, when light travels from a smaller index of refraction towards a larger index of refraction, there is no phase change upon reflection.

Question 5

In the two-slit experiment, for the condition of bright fringes, the value of m = +2 corresponds to a path difference of λ.

Accepted Answer

In the two-slit experiment, the condition for bright fringes (constructive interference) is given by the path difference being an integer multiple of the wavelength, mλ. For m = +2, the path difference is 2λ, not λ.

Question 6

If the first maximum of one circular diffraction pattern passes through the center of a second diffraction pattern, the two sources responsible for the pattern will appear to be a single source.

Accepted Answer

The answer of If the first maximum of one circular...

Question 7

The law of reflection, as well as the law of refraction, can be derived using Huygens' principle.

Accepted Answer

Huygens' principle states that each point on a wavefront can be considered as a source of secondary wavelets, which spread out in all directions at the speed of light. Using this principle, one can derive the laws of reflection and refraction, which govern how waves change direction upon encountering a boundary between two different media. Therefore, the statement is true.

Question 8

In the experiment for interference using the concept of air wedge, the point where the glass plates touch in an air wedge is a dark fringe.

Accepted Answer

When light waves pass through the air wedge, they undergo interference, resulting in a pattern of bright and dark fringes. The point where the glass plates touch is a point of minimum thickness and maximum separation, causing destructive interference and a dark fringe to be formed.

Question 9

The interference pattern observed in Newton's rings experiment is because of the path difference between the top surface and the bottom surface of the air between the pieces of glass.

Accepted Answer

The interference pattern observed in Newton's rings experiment is due to the path difference between the top and bottom surfaces of the air film formed between the curved surface of a plano-convex lens and a flat glass plate pressed against it. The path difference leads to constructive and destructive interference of the incident light, resulting in a pattern of bright and dark rings.

Question 10

If two or more sources of light are to show interference patterns, they must be coherent.

Accepted Answer

This is true. Interference patterns can only be seen between two or more sources of coherent light waves. Coherent light waves are those that have the same frequency and are in phase with each other.

Question 11

Coherent sources of light have a varying phase difference.

Accepted Answer

Coherent sources of light have a constant phase difference, which allows them to produce a stable interference pattern.

Question 12

In the two-slit experiment, for the condition of dark fringes, the value of m = +1 corresponds to a path difference of 3λ/2.

Accepted Answer

For dark fringes, the path difference between the two slits should be an odd multiple of half of the wavelength λ, i.e., (2n - 1)λ/2, where n is an integer. So for m = +1, the path difference would be λ/2, not 3λ/2.

Question 13

Interference is the superposition of two or more waves.

Accepted Answer

Interference is the combination of waves that results in a net wave amplitude that is either greater or less than the amplitude of the individual waves. This can occur when two or more waves are in the same place at the same time and their wave peaks and troughs overlap.

Question 14

In a single-slit diffraction experiment, the central maximum is broadened if the wavelength of light increased.

Accepted Answer

The width of the central maximum in a single-slit diffraction pattern is proportional to the wavelength of the light source used. As the wavelength increases, the central maximum becomes broader. This is known as the diffraction effect and is a well-established phenomenon in physics. Therefore, option A is correct.

Question 15

In the two-slit experiment, for the condition of dark fringes, the value of m = +2 corresponds to a path difference of 3λ/2.

Accepted Answer

This statement is true. The path difference between the two slits for the condition of dark fringes when m = +2 is given by 2d sin θ = mλ, where d is the distance between the slits, θ is the angle between the incident light and the normal to the slits, m is the order of the fringe, and λ is the wavelength of the light. Substituting m = +2, we get 2d sin θ = 2λ, which gives a path difference of 3λ/2 for a single slit.

Question 16

For two beams of light traveling different distances in reaching a point, and to form maximum constructive interference at that point, the beams must travel paths that differ by a whole number of wavelengths.

Accepted Answer

This is the principle of coherent and constructive interference in which the path difference between two waves must be a whole number of wavelengths for maximum constructive interference to occur.

Question 17

Two coherent light sources are characterized by
A) having the same amplitude.
B) having the same frequency.
C) having the same wavelength.
D) having the same velocity.
E) having the same frequency and maintaining a constant phase difference.

Accepted Answer

Coherence between two sources refers to the constancy of the phase difference between their waves. Choice E states that the sources have the same frequency and maintain a constant phase difference, which is the definition of coherence. Choices A, B, and C are incorrect because two sources can be coherent even if they have different amplitudes, frequencies, or wavelengths. Choice D is incorrect because the velocity of light is constant in a given medium and is not a factor that characterizes coherence between two sources.

Question 18

Which one of the following properties of light is evidence of the wave nature of light?
A) Reflection of light
B) Refraction of light
C) Emission of light
D) Dispersion of light
E) Interference of light

Accepted Answer

Interference of light is a phenomenon that can only be explained by the wave nature of light, as it involves the superposition of light waves leading to constructive and destructive interference patterns.

Question 19

The wavelength of light is important for thin film interference to occur within the film itself.

Accepted Answer

Thin film interference occurs when light waves reflect off of the top and bottom surfaces of a thin film, interfering with each other. The thickness of the film and the wavelength of the light determine the interference pattern. A difference in thickness of the film by a quarter wavelength of the light results in destructive interference, while a half wavelength results in constructive interference. Therefore, the wavelength of light is crucial for thin film interference to occur.

Question 20

The interference of light is because of its particle nature as suggested by Sir Isaac Newton.

Accepted Answer

The interference of light is actually due to its wave nature, as discovered by Thomas Young in his double-slit experiment. Newton's hypothesis that light consisted of particles (or "corpuscles") was largely rejected in favor of the wave theory of light.

Quiz 28: Physical Optics: Interference and Diffraction