Question 1

A double-slit interference experiment is performed in the air. Later, the same apparatus is immersed in benzene (which has an index of refraction of 1.50), and the experiment is repeated. When the apparatus is in benzene, you observe that the interference fringes are
A) more closely spaced than when the apparatus is in air.
B) equally spaced as when the apparatus is in air.
C) more widely spaced than when the apparatus is in air.

Accepted Answer

The wavelength of light decreases when it moves from air into a medium with a higher index of refraction, such as benzene. This decrease in wavelength leads to more closely spaced interference fringes, as the fringe spacing is directly related to the wavelength of the light.

Question 2

A single-slit diffraction pattern is formed on a distant screen. Assuming the angles involved are small, by what factor will the width of the central bright spot on the screen change if the slit width is doubled?
A) It will be cut to one-quarter its original size.
B) It will be cut in half.
C) It will double.
D) It will become four times as large.
E) It will become eight times as large.

Accepted Answer

The width of the central bright spot is directly proportional to the width of the slit. If the slit width is doubled, the width of the central bright spot will also double. Therefore, the answer is B, which states that the width of the central bright spot will be cut in half.

Question 3

Radio waves are diffracted by large objects such as buildings, whereas light is not noticeably diffracted. Why is this?
A) Radio waves are unpolarized, whereas light is normally polarized.
B) The wavelength of light is much smaller than the wavelength of radio waves.
C) The wavelength of light is much greater than the wavelength of radio waves.
D) Radio waves are coherent and light is usually not coherent.
E) Radio waves are polarized, whereas light is usually unpolarized.

Accepted Answer

The amount of diffraction depends on the size of the object relative to the wavelength of the wave. Since the wavelength of radio waves is much larger than the wavelength of light, they are diffracted more by large objects such as buildings.

Question 4

If a sheet containing a single thin slit is heated (without damaging it) and therefore expands, what happens to the width of the central bright diffraction region on a distant screen?
A) It gets narrower.
B) It gets wider.
C) It doesn't change.

Accepted Answer

The width of the central bright diffraction region on a distant screen is directly proportional to the width of the slit. When the slit expands due to heating, its width increases, which leads to the central bright diffraction region becoming wider. Therefore, the correct choice is B.

Question 5

What principle is responsible for light spreading as it passes through a narrow slit?
A) refraction
B) polarization
C) diffraction
D) dispersion

Accepted Answer

Diffraction is the principle responsible for light spreading as it passes through a narrow slit. This occurs because light waves spread out when they encounter an object with a size comparable to or smaller than their wavelength, causing the wave to bend and spread out into a pattern of bright and dark bands.

Question 6

Two beams of coherent light start out at the same point in phase and travel different paths to arrive at point P. If the maximum constructive interference is to occur at point P, the two beams must travel paths that differ by
A) a whole number of wavelengths.
B) an odd number of half-wavelengths.
C) a whole number of half-wavelengths.

Accepted Answer

To achieve maximum constructive interference, the peak of one wave must align with the peak of the other wave. This occurs when the path difference between the two waves is equal to a whole number of wavelengths (i.e. the waves are in phase). If the path difference were a half-wavelength or a whole number of half-wavelengths, the waves would be out of phase and maximum constructive interference would not occur.

Question 7

A single-slit diffraction pattern is formed on a distant screen. Assuming the angles involved are small, by what factor will the width of the central bright spot on the screen change if the wavelength of the illuminating light is doubled?
A) It will be cut to one-quarter its original size.
B) It will be cut in half.
C) It will double.
D) It will become four times as large.
E) It will become eight times as large.

Accepted Answer

The width of the central bright spot in a single-slit diffraction pattern is directly proportional to the wavelength of the light used. Therefore, if the wavelength is doubled, the width of the central bright spot will also double.

Question 8

Two light sources are said to be coherent if they are
A) of the same frequency.
B) of the same frequency, and maintain a constant phase difference.
C) of the same amplitude, and maintain a constant phase difference.
D) of the same frequency and amplitude.

Accepted Answer

Coherent sources have the same frequency and maintain a constant phase difference, which means that their waves have a consistent pattern of interference. This results in stable and well-defined interference patterns, which can be used for various applications such as interferometry and holography. Having the same amplitude is not a requirement for coherence, as long as the phase difference remains constant. Having the same frequency and amplitude is not sufficient for coherence, as the phase difference can vary arbitrarily between the two sources.

Question 9

If the index of refraction of a material is 2, this means that light travels
A) 2 times as fast in air as it does in vacuum.
B) 2 times as fast in the material as it does in air.
C) 2 times as fast in vacuum as it does in the material.
D) 2 times as fast in the material than it does in vacuum.
E) 1/2 as fast in air as it does in the material.

Accepted Answer

The index of refraction (n) of a material is defined as the ratio of the speed of light in vacuum (c) to the speed of light in the material (v), i.e., n = c/v. Therefore, if the index of refraction is 2, it means light travels 2 times as fast in vacuum as it does in the material.

Question 10

When light travels from air into water,
A) its velocity, wavelength and frequency all change.
B) its velocity changes, but its frequency and wavelength do not change.
C) its frequency changes, but its velocity and wavelength do not change.
D) its velocity and wavelength change, but its frequency does not change.
E) its wavelength changes, but its velocity and frequency do not change.

Accepted Answer

When light moves from air into water, its speed decreases because water has a higher refractive index than air. This change in speed also leads to a change in wavelength. However, the frequency of light remains constant because it is determined by the source of the light and does not change when light moves between mediums.

Question 11

Monochromatic coherent light shines through a pair of slits. If the wavelength of the light is decreased, which of the following statements are true of the resulting interference pattern? (There could be more than one correct choice.)
A) The distance between the maxima stays the same.
B) The distance between the maxima decreases.
C) The distance between the minima stays the same.
D) The distance between the minima increases.
E) The distance between the minima decreases.

Accepted Answer

The distance between the maxima in an interference pattern is given by the equation d*sin(theta) = m*lambda, where d is the distance between the slits, theta is the angle between the central maximum and the mth maximum, lambda is the wavelength of the light, and m is an integer. Since the distance between the slits and the angle between the maxima are constant, decreasing the wavelength of the light will decrease the distance between the maxima.

Similarly, the distance between the minima in an interference pattern is given by the equation d*sin(theta) = (m + 1/2)*lambda. Since the distance between the slits and the angle between the minima are constant, decreasing the wavelength of the light will decrease the distance between the minima. Therefore, B and E are the correct choices.

Question 12

If a sheet containing a single slit is heated (without damaging it) and therefore expands, what happens to the angular location of the first-order diffraction minimum?
A) It moves toward the centerline.
B) It moves away from the centerline.
C) It doesn't change.

Accepted Answer

When the sheet expands, the slit also expands causing the diffracted waves to bend less. This reduces the diffraction angle, making the first-order diffraction minimum move toward the centerline.

Question 13

In a double-slit interference experiment you are asked to use laser light of different wavelengths and determine the separation between adjacent maxima. You observe that this separation is greatest when you illuminate the double slit with
A) blue light.
B) green light.
C) yellow light.
D) red light.
E) The separation is the same for all wavelengths.

Accepted Answer

The separation between adjacent maxima in a double-slit interference pattern is given by the equation d*sin(theta) = m*wavelength, where d is the slit spacing, theta is the angle between the incident beam and the normal to the plane of the slits, m is the order of the maximum, and wavelength is the wavelength of the light used. Since the separation is proportional to the wavelength, the separation will be greatest for the longest wavelength used, which is red light. Therefore, the correct answer is D.

Question 14

Two beams of coherent light start out at the same point in phase and travel different paths to arrive at point P. If the maximum destructive interference is to occur at point P, the two beams must travel paths that differ by
A) a whole number of wavelengths.
B) an odd number of half-wavelengths.
C) a whole number of half-wavelengths.

Accepted Answer

For maximum destructive interference, the two waves must be exactly out of phase, which means that one wave must be shifted by half a wavelength (180 degrees) relative to the other. Therefore, the two beams must travel paths that differ by an odd number of half-wavelengths. Choice B is the only option that satisfies this condition.

Question 15

What do we mean when we say that two light rays striking a screen are in phase with each other?
A) When the electric field due to one is a maximum, the electric field due to the other is also a maximum, and this relation is maintained as time passes.
B) They are traveling at the same speed.
C) They have the same wavelength.
D) They alternately reinforce and cancel each other.

Accepted Answer

When two light rays are in phase with each other, it means that the electric field due to one is a maximum when the electric field due to the other is also a maximum, and this relation is maintained as time passes. This results in constructive interference, leading to a brighter spot on the screen where they meet.

Question 16

If a sheet containing two very thin slits is heated (without damaging it), what happens to the angular location of the first-order interference minimum?
A) It moves toward the centerline.
B) It moves away from the centerline.
C) It doesn't change.

Accepted Answer

Heating the sheet will cause it to expand, which will increase the distance between the two slits. As the distance between the slits increases, the angle of diffraction (which determines the location of the interference minimum) decreases. Therefore, the first-order interference minimum moves toward the centerline.

Question 17

In a single-slit diffraction experiment, the width of the slit through which light passes is reduced. What happens to the width of the central bright fringe in the resulting diffraction pattern?
A) It stays the same.
B) It becomes narrower.
C) It becomes wider.

Accepted Answer

When the width of the slit is reduced, the diffraction effect becomes more pronounced, causing the central bright fringe to become wider. This is because the angle of diffraction increases as the slit width decreases, according to the relationship given by the diffraction formula.

Question 18

In a double-slit experiment, it is observed that the distance between adjacent maxima on a remote screen is 1.0 cm. What happens to the distance between adjacent maxima when the slit separation is cut in half?
A) It increases to 2.0 cm.
B) It increases to 4.0 cm.
C) It decreases to 0.50 cm.
D) It decreases to 0.25 cm.
E) None of these choices are correct.

Accepted Answer

The distance between adjacent maxima in a double-slit experiment is directly proportional to the slit separation. Halving the slit separation doubles the distance between maxima.

Question 19

A light beam has speed c in vacuum and speed v in a certain plastic. The index of refraction n of this plastic is A) n = cv. B) n = (v/c)². C) n = v/c. D) n = c/v. E) n = (c/v)².

Accepted Answer

According to Snell's law, the index of refraction of a medium is given by n = c/v, where c is the speed of light in vacuum and v is the speed of light in that medium. Therefore, option D is the correct choice.

Question 20

Monochromatic coherent light shines through a pair of slits. If the distance between these slits is decreased, which of the following statements are true of the resulting interference pattern? (There could be more than one correct choice.)
A) The distance between the maxima stays the same.
B) The distance between the maxima decreases.
C) The distance between the minima stays the same.
D) The distance between the minima increases.
E) The distance between the maxima increases.

Accepted Answer

The answer of Monochromatic coherent light shines through a pair...

Quiz 17: Wave Optics

A double-slit interference experiment is performed in the air. Later, the same apparatus is immersed in benzene (which has an index of refraction of 1.50) , and the experiment is repeated. When the apparatus is in benzene, you observe that the interference fringes are

A single-slit diffraction pattern is formed on a distant screen. Assuming the angles involved are small, by what factor will the width of the central bright spot on the screen change if the slit width is doubled?

Radio waves are diffracted by large objects such as buildings, whereas light is not noticeably diffracted. Why is this?

If a sheet containing a single thin slit is heated (without damaging it) and therefore expands, what happens to the width of the central bright diffraction region on a distant screen?

What principle is responsible for light spreading as it passes through a narrow slit?

Two beams of coherent light start out at the same point in phase and travel different paths to arrive at point P. If the maximum constructive interference is to occur at point P, the two beams must travel paths that differ by

A single-slit diffraction pattern is formed on a distant screen. Assuming the angles involved are small, by what factor will the width of the central bright spot on the screen change if the wavelength of the illuminating light is doubled?

Two light sources are said to be coherent if they are

If the index of refraction of a material is 2, this means that light travels

When light travels from air into water,

Monochromatic coherent light shines through a pair of slits. If the wavelength of the light is decreased, which of the following statements are true of the resulting interference pattern? (There could be more than one correct choice.)

If a sheet containing a single slit is heated (without damaging it) and therefore expands, what happens to the angular location of the first-order diffraction minimum?

In a double-slit interference experiment you are asked to use laser light of different wavelengths and determine the separation between adjacent maxima. You observe that this separation is greatest when you illuminate the double slit with

Two beams of coherent light start out at the same point in phase and travel different paths to arrive at point P. If the maximum destructive interference is to occur at point P, the two beams must travel paths that differ by

What do we mean when we say that two light rays striking a screen are in phase with each other?

If a sheet containing two very thin slits is heated (without damaging it) , what happens to the angular location of the first-order interference minimum?

In a single-slit diffraction experiment, the width of the slit through which light passes is reduced. What happens to the width of the central bright fringe in the resulting diffraction pattern?

In a double-slit experiment, it is observed that the distance between adjacent maxima on a remote screen is 1.0 cm. What happens to the distance between adjacent maxima when the slit separation is cut in half?

A light beam has speed c in vacuum and speed v in a certain plastic. The index of refraction n of this plastic is

Monochromatic coherent light shines through a pair of slits. If the distance between these slits is decreased, which of the following statements are true of the resulting interference pattern? (There could be more than one correct choice.)