Chapter 24: The Wave Nature Of Light
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Questions and Answers
- 1.
Which of the following is a false statement?
- A.
All points on a given wave front have the same phase.
- B.
Rays are always perpendicular to wave fronts.
- C.
All wave fronts have the same amplitude.
- D.
The spacing between adjacent wave fronts is one-half wavelength.
Correct Answer
C. All wave fronts have the same amplitude.Explanation
The statement "All wave fronts have the same amplitude" is false because wave fronts represent the crests or troughs of a wave, while amplitude refers to the height or intensity of the wave. Wave fronts can have different amplitudes depending on the energy or magnitude of the wave at a particular point.Rate this question:
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- 2.
The wave theory of light is attributed to
- A.
Christian Huygens.
- B.
Isaac Newton.
- C.
Max Planck.
- D.
Albert Einstein.
Correct Answer
A. Christian Huygens.Explanation
The wave theory of light is attributed to Christian Huygens. Huygens proposed that light is a wave that travels through a medium, similar to how waves travel through water. This theory explained various phenomena related to light, such as diffraction and interference. Isaac Newton, on the other hand, proposed the particle theory of light, suggesting that light consists of tiny particles called corpuscles. Max Planck and Albert Einstein made significant contributions to the field of physics, but their work was primarily related to quantum mechanics and the theory of relativity, respectively, rather than the wave theory of light.Rate this question:
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- 3.
The particle theory of light is attributed to
- A.
Christian Huygens.
- B.
Isaac Newton.
- C.
Max Planck.
- D.
Albert Einstein.
Correct Answer
B. Isaac Newton.Explanation
Isaac Newton is attributed to the particle theory of light. He proposed that light is made up of tiny particles called corpuscles. Newton's theory suggested that these corpuscles travel in straight lines and can be reflected and refracted. This theory was later challenged by the wave theory of light proposed by Christian Huygens, which gained more acceptance. However, Newton's particle theory laid the foundation for further understanding of the nature of light. Max Planck and Albert Einstein made significant contributions to the field of physics but were not specifically associated with the particle theory of light.Rate this question:
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- 4.
When a light wave enters into a medium of different optical density,
- A.
Its speed and frequency change.
- B.
Its speed and wavelength change.
- C.
Its frequency and wavelength change.
- D.
Its speed, frequency, and wavelength change.
Correct Answer
B. Its speed and wavelength change.Explanation
When a light wave enters into a medium of different optical density, its speed and wavelength change. This is because the speed of light is dependent on the optical density of the medium it is passing through. As the light wave enters a medium with a different optical density, it experiences a change in speed, causing its wavelength to also change according to the equation speed = frequency x wavelength. The frequency of the light wave, however, remains constant as it is a characteristic property of the light wave itself and does not depend on the medium it is passing through.Rate this question:
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- 5.
When a beam of light (wavelength = 590 nm), originally traveling in air, enters a piece of glass (index of refraction 1.50), its frequency
- A.
Increases by a factor of 1.50.
- B.
Is reduced to 2/3 its original value.
- C.
Is unaffected.
- D.
None of the given answers
Correct Answer
C. Is unaffected.Explanation
When a beam of light enters a different medium, its wavelength changes but its frequency remains constant. The speed of light in a medium is given by the equation v = c/n, where v is the speed of light in the medium, c is the speed of light in a vacuum, and n is the refractive index of the medium. As the light enters the glass with a refractive index of 1.50, its speed decreases, causing its wavelength to decrease as well. However, since frequency is inversely proportional to wavelength, the frequency of the light remains unaffected. Therefore, the correct answer is that the frequency is unaffected.Rate this question:
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- 6.
When a beam of light (wavelength = 590 nm), originally traveling in air, enters a piece of glass (index of refraction 1.50), its wavelength
- A.
Increases by a factor of 1.50.
- B.
Is reduced to 2/3 its original value.
- C.
Is unaffected.
- D.
None of the given answers
Correct Answer
B. Is reduced to 2/3 its original value.Explanation
When a beam of light enters a medium with a higher refractive index, such as glass, its wavelength is reduced. This is known as wavelength reduction or wavelength shift. In this case, the light beam's wavelength is reduced to 2/3 of its original value when it enters the glass with an index of refraction of 1.50. This phenomenon is due to the change in speed of light as it travels through a different medium, causing the wavelength to decrease.Rate this question:
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- 7.
What principle is responsible for light spreading as it passes through a narrow slit?
- A.
Refraction
- B.
Polarization
- C.
Diffraction
- D.
Interference
Correct Answer
C. DiffractionExplanation
Diffraction is the principle responsible for light spreading as it passes through a narrow slit. Diffraction occurs when light waves encounter an obstacle or aperture that is comparable in size to the wavelength of the light. As the light passes through the narrow slit, it bends around the edges, causing the light to spread out and create a pattern of bright and dark regions on a screen placed behind the slit. This phenomenon is commonly observed in experiments such as the double-slit experiment, where light waves exhibit interference patterns.Rate this question:
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- 8.
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 plane 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.
Correct Answer
B. The wavelength of light is much smaller than the wavelength of radio waves.Explanation
The correct answer is that the wavelength of light is much smaller than the wavelength of radio waves. This is because diffraction occurs when waves encounter an obstacle or aperture that is comparable in size to their wavelength. Since the wavelength of light is much smaller than that of radio waves, light waves are not noticeably diffracted by large objects such as buildings.Rate this question:
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- 9.
What principle is responsible for alternating light and dark bands when light passes through two or more narrow slits?
- A.
Refraction
- B.
Polarization
- C.
Dispersion
- D.
Interference
Correct Answer
D. InterferenceExplanation
Interference is the principle responsible for alternating light and dark bands when light passes through two or more narrow slits. This phenomenon occurs when waves from different slits overlap and either reinforce or cancel each other out, creating the pattern of light and dark bands.Rate this question:
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- 10.
Two light sources are said to be coherent if they
- A.
Are of the same frequency.
- B.
Are of the same frequency, and maintain a constant phase difference.
- C.
Are of the same amplitude, and maintain a constant phase difference.
- D.
Are of the same frequency and amplitude.
Correct Answer
B. Are of the same frequency, and maintain a constant phase difference.Explanation
Two light sources are said to be coherent if they are of the same frequency and maintain a constant phase difference. Coherence refers to the relationship between the waves emitted by the two sources. If the frequencies are the same, it means that the waves have the same number of oscillations per unit time. Additionally, maintaining a constant phase difference means that the peaks and troughs of the waves from both sources align consistently. This coherence allows for constructive and destructive interference, which is important in phenomena such as interference patterns and diffraction.Rate this question:
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- 11.
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.
Correct Answer
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.Explanation
When we say that two light rays striking a screen are in phase with each other, it means that the electric field due to one light ray is at its maximum and the electric field due to the other light ray is also at its maximum. This relationship between the electric fields of the two light rays is maintained as time passes. In other words, the peaks and troughs of the electric fields of the two light rays align with each other, resulting in constructive interference and a brighter image on the screen. This indicates that the two light rays have the same phase and are synchronized in their oscillations.Rate this question:
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- 12.
Two beams of coherent light travel different paths arriving at point P. If the maximum constructive interference is to occur at point P, the two beams must
- A.
Travel paths that differ by a whole number of wavelengths.
- B.
Travel paths that differ by an odd number of half-wavelengths.
Correct Answer
A. Travel paths that differ by a whole number of wavelengths.Explanation
To achieve maximum constructive interference at point P, the two beams of coherent light must have their crests and troughs align perfectly. This occurs when the path difference between the two beams is a whole number of wavelengths. When the path difference is an odd number of half-wavelengths, the crests of one beam align with the troughs of the other, resulting in destructive interference rather than constructive interference. Therefore, the correct answer is that the two beams must travel paths that differ by a whole number of wavelengths.Rate this question:
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- 13.
Two beams of coherent light travel different paths arriving at point P. If the maximum destructive interference is to occur at point P, the two beams must
- A.
Travel paths that differ by a whole number of wavelengths.
- B.
Travel paths that differ by an odd number of half-wavelengths.
Correct Answer
B. Travel paths that differ by an odd number of half-wavelengths.Explanation
To achieve destructive interference at point P, the two beams of coherent light must have a phase difference of half a wavelength. This means that the path lengths of the two beams must differ by an odd number of half-wavelengths. This is because when the two waves meet, the crests of one wave will coincide with the troughs of the other wave, resulting in destructive interference. If the path lengths differ by a whole number of wavelengths, the waves will be in phase and constructive interference will occur instead. Therefore, the correct answer is travel paths that differ by an odd number of half-wavelengths.Rate this question:
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- 14.
At the first maxima on either side of the central bright spot in a double-slit experiment, light from each opening arrives
- A.
In phase.
- B.
90° out of phase.
- C.
180° out of phase.
- D.
None of the given answers
Correct Answer
A. In phase.Explanation
At the first maxima on either side of the central bright spot in a double-slit experiment, light from each opening arrives in phase. This means that the crests and troughs of the waves from both slits align perfectly, resulting in constructive interference and a bright fringe. In-phase arrival occurs when the path lengths from both slits to the point of observation are equal, causing the waves to be in sync. This is why the light from each opening adds up and results in a bright spot.Rate this question:
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- 15.
At the first minima on either side of the central bright spot in a double-slit experiment, light from each opening arrives
- A.
In phase.
- B.
90° out of phase.
- C.
180° out of phase.
- D.
None of the given answers
Correct Answer
C. 180° out of phase.Explanation
At the first minima on either side of the central bright spot in a double-slit experiment, the light waves from each opening interfere destructively. This means that the crests of one wave align with the troughs of the other wave, resulting in a phase difference of 180°. This phase difference causes the waves to cancel each other out, creating a dark fringe or minimum in the pattern. Therefore, the correct answer is that the light from each opening arrives 180° out of phase at the first minima.Rate this question:
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- 16.
At the second maxima on either side of the central bright spot in a double-slit experiment, light from
- A.
Each opening travels the same distance.
- B.
One opening travels twice as far as light from the other opening.
- C.
One opening travels one wavelength of light farther than light from the other opening.
- D.
One opening travels two wavelengths of light farther than light from the other opening.
Correct Answer
D. One opening travels two wavelengths of light farther than light from the other opening.Explanation
In a double-slit experiment, the second maxima on either side of the central bright spot occurs when the path difference between the two slits is equal to two wavelengths of light. This means that one opening travels two wavelengths of light farther than the other opening. This path difference leads to constructive interference, resulting in a bright spot.Rate this question:
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- 17.
In a Young's double slit experiment, if the separation between the slits decreases, what happens to the distance between the interference fringes?
- A.
It decreases.
- B.
It increases.
- C.
It remains the same.
- D.
There is not enough information to determine.
Correct Answer
B. It increases.Explanation
When the separation between the slits decreases in a Young's double slit experiment, the distance between the interference fringes increases. This is because the interference pattern is determined by the wavelength of the light and the distance between the slits. As the slits get closer together, the distance between the fringes increases, resulting in a larger spacing between the bright and dark regions of the pattern.Rate this question:
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- 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.
Correct Answer
A. It increases to 2.0 cm.Explanation
When the slit separation is cut in half, the distance between adjacent maxima on the remote screen will increase to 2.0 cm. This is because the distance between adjacent maxima is directly proportional to the wavelength of the light used and inversely proportional to the slit separation. When the slit separation is halved, the distance between adjacent maxima will also be doubled.Rate this question:
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- 19.
One beam of coherent light travels path P1 in arriving at point Q and another coherent beam travels path P2 in arriving at the same point. If these two beams are to interfere destructively, the path difference P1 - P2 must be equal to
- A.
An odd number of half-wavelengths.
- B.
Zero.
- C.
A whole number of wavelengths.
- D.
A whole number of half-wavelengths.
Correct Answer
A. An odd number of half-wavelengths.Explanation
When two coherent beams of light interfere destructively, it means that the crests of one beam coincide with the troughs of the other beam, resulting in cancellation of the waves. This happens when the path difference between the two beams is equal to an odd number of half-wavelengths. In other words, if the path difference is an odd number of half-wavelengths, the waves will be out of phase and interfere destructively. Therefore, the correct answer is "an odd number of half-wavelengths."Rate this question:
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- 20.
If a wave from one slit of a Young's double slit experiment arrives at a point on the screen one-half wavelength behind the wave from the other slit, which is observed at that point?
- A.
Bright fringe
- B.
Dark fringe
- C.
Gray fringe
- D.
Multi-colored fringe
Correct Answer
B. Dark fringeExplanation
When the wave from one slit arrives at a point on the screen one-half wavelength behind the wave from the other slit, they will be out of phase and interfere destructively. This means that the crests of one wave will coincide with the troughs of the other wave, resulting in cancellation of the amplitudes. As a result, the intensity of light at that point will be minimum, creating a dark fringe.Rate this question:
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- 21.
Why would it be impossible to obtain interference fringes in a double-slit experiment if the separation of the slits is less than the wavelength of the light used?
- A.
The very narrow slits required would generate many different wavelengths, thereby washing out the interference pattern.
- B.
The two slits would not emit coherent light.
- C.
The fringes would be too close together.
- D.
In no direction could a path difference as large as one wavelength be obtained, and this is needed if a bright fringe, in addition to the central fringe, is to be observed.
Correct Answer
D. In no direction could a path difference as large as one wavelength be obtained, and this is needed if a bright fringe, in addition to the central fringe, is to be observed.Explanation
If the separation of the slits is less than the wavelength of the light used, it would be impossible to obtain interference fringes because in no direction could a path difference as large as one wavelength be obtained. In order to observe a bright fringe, in addition to the central fringe, a path difference of at least one wavelength is needed. Since the slits are very narrow, they would generate many different wavelengths, which would wash out the interference pattern. Additionally, the two slits would not emit coherent light.Rate this question:
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- 22.
The separation between adjacent maxima in a double-slit interference pattern using monochromatic light is
- A.
Greatest for red light.
- B.
Greatest for green light.
- C.
Greatest for blue light.
- D.
D) the same for all colors of light.
Correct Answer
A. Greatest for red light.Explanation
The separation between adjacent maxima in a double-slit interference pattern is determined by the wavelength of the light. The longer the wavelength, the greater the separation between the maxima. Red light has the longest wavelength among the given options, so the separation between adjacent maxima is greatest for red light.Rate this question:
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- 23.
The principle which explains why a prism separates white light into different colors is
- A.
Refraction.
- B.
Polarization.
- C.
Dispersion.
- D.
Total internal reflection.
Correct Answer
C. Dispersion.Explanation
Dispersion is the principle that explains why a prism separates white light into different colors. When white light passes through a prism, it is refracted at different angles depending on its wavelength. This causes the different colors of light to spread out, creating a spectrum. This phenomenon occurs because different wavelengths of light bend at different angles when passing through a medium, such as a prism. Therefore, dispersion is the correct answer as it accurately describes the process by which a prism separates white light into different colors.Rate this question:
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- 24.
The principle which allows a rainbow to form is
- A.
Refraction.
- B.
Polarization.
- C.
Dispersion.
- D.
Total internal reflection.
Correct Answer
C. Dispersion.Explanation
Dispersion is the principle that allows a rainbow to form. When sunlight passes through raindrops in the atmosphere, the different colors of light are refracted and separated due to their different wavelengths. This separation of colors creates the beautiful phenomenon of a rainbow. Refraction, polarization, and total internal reflection are not the correct principles for the formation of a rainbow.Rate this question:
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- 25.
White light is
- A.
Light of wavelength 550 nm, in the middle of the visible spectrum.
- B.
A mixture of all frequencies.
- C.
A mixture of red, green, and blue light.
- D.
The term used to describe very bright light.
- E.
The opposite (or complementary color) of black light.
Correct Answer
B. A mixture of all frequencies.Explanation
White light is a mixture of all frequencies. This means that it contains all the colors of the visible spectrum, from red to violet. When white light passes through a prism, it is dispersed into its component colors, creating a rainbow. This is because each color of light has a different wavelength, and the prism separates them based on their wavelengths. Therefore, white light is not just a single color, but a combination of all the colors of the visible spectrum.Rate this question:
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- 26.
Light with wavelength slightly shorter than 400 nm is called
- A.
Ultraviolet light.
- B.
Visible light.
- C.
Infrared light.
- D.
None of the given answers
Correct Answer
A. Ultraviolet light.Explanation
Ultraviolet light is the correct answer because light with a wavelength slightly shorter than 400 nm falls within the ultraviolet spectrum. Ultraviolet light is not visible to the human eye but is commonly found in sunlight and has various applications in medicine, sterilization, and fluorescence.Rate this question:
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- 27.
Light with wavelength slightly longer than 750 nm is called
- A.
Ultraviolet light.
- B.
Visible light.
- C.
Infrared light.
- D.
None of the given answers
Correct Answer
C. Infrared light.Explanation
Infrared light refers to light with a wavelength slightly longer than 750 nm. Ultraviolet light has a shorter wavelength, while visible light falls within the range of wavelengths that can be detected by the human eye. Therefore, the correct answer is infrared light.Rate this question:
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- 28.
Which color of light undergoes the greatest refraction when passing from air to glass?
- A.
Red
- B.
Yellow
- C.
Green
- D.
Violet
Correct Answer
D. VioletExplanation
When light passes from air to glass, it undergoes refraction, which is the bending of light as it enters a new medium. The amount of refraction depends on the wavelength of the light. Violet light has the shortest wavelength among the colors listed, which means it has a higher frequency. Higher frequency light bends more when it passes from air to glass, resulting in greater refraction. Therefore, violet light undergoes the greatest refraction compared to red, yellow, and green light.Rate this question:
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- 29.
Which color of light undergoes the smallest refraction when passing from air to glass?
- A.
Red
- B.
Yellow
- C.
Green
- D.
Violet
Correct Answer
A. RedExplanation
Red light undergoes the smallest refraction when passing from air to glass. This is because red light has the longest wavelength among the given options. According to the principle of refraction, light with longer wavelengths bends less when it passes from one medium to another. Therefore, red light experiences the smallest change in direction when it enters the glass, resulting in the smallest refraction.Rate this question:
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- 30.
A beam of white light is incident on a thick glass plate with parallel sides, at an angle between 0° and 90° with the normal. Which color emerges from the other side first?
- A.
Red
- B.
Green
- C.
Violet
- D.
None of the given; all colors emerge at the same time.
Correct Answer
D. None of the given; all colors emerge at the same time.Explanation
When white light passes through a thick glass plate, it undergoes dispersion, which means that the different colors in the white light are separated. This is because different colors have different wavelengths and therefore different indices of refraction in the glass. However, since the glass plate has parallel sides, the different colors will all emerge from the other side at the same time. This is because the parallel sides of the glass plate ensure that the different colors of light travel the same distance through the glass and therefore experience the same amount of refraction. Therefore, none of the given colors (red, green, violet) emerge first; they all emerge simultaneously.Rate this question:
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- 31.
A person gazes at a very distant light source. If she now holds up two fingers, with a very small gap between them, and looks at the light source, she will see
- A.
The same thing as without the fingers, but dimmer.
- B.
A series of bright spots.
- C.
A sequence of closely spaced bright lines.
- D.
A hazy band of light varying from red at one side to blue or violet at the other.
Correct Answer
C. A sequence of closely spaced bright lines.Explanation
When a person gazes at a very distant light source and holds up two fingers with a small gap between them, they will see a phenomenon called diffraction. Diffraction causes the light waves to bend around the edges of the fingers, creating a pattern of closely spaced bright lines. This occurs because the gap between the fingers acts as a narrow slit, causing the light to spread out and interfere with itself, resulting in the formation of the bright lines.Rate this question:
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- 32.
In a single slit diffraction experiment, if the width of the slit increases, what happens to the width of the central maximum on a screen?
- A.
It increases.
- B.
It decreases.
- C.
It remains the same.
- D.
There is not enough information to determine.
Correct Answer
B. It decreases.Explanation
When the width of the slit increases in a single slit diffraction experiment, the width of the central maximum on a screen decreases. This is because a wider slit allows more diffraction of light, resulting in a larger diffraction pattern. As a result, the central maximum becomes narrower.Rate this question:
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- 33.
Consider two diffraction gratings; one has 4000 lines per cm and the other one has 6000 lines per cm. Make a statement comparing the dispersion of the two gratings.
- A.
The 4000-line grating produces the greater dispersion.
- B.
The 6000-line grating produces the greater dispersion.
- C.
Both gratings produce the same dispersion, but the orders are sharper for the 4000-line grating.
- D.
Both gratings produce the same dispersion, but the orders are sharper for the 6000-line grating.
Correct Answer
B. The 6000-line grating produces the greater dispersion.Explanation
The dispersion of a diffraction grating is determined by the number of lines per unit length. In this case, the 6000-line grating has a higher number of lines per cm compared to the 4000-line grating. Therefore, the 6000-line grating produces greater dispersion.Rate this question:
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- 34.
Consider two diffraction gratings with the same slit separation, the only difference being that one grating has 3 slits and the other 4 slits. If both gratings are illuminated with a beam of the same monochromatic light, make a statement concerning the separation between the orders.
- A.
The grating with 3 slits produces the greater separation between orders.
- B.
The grating with 4 slits produces the greater separation between orders.
- C.
Both gratings produce the same separation between orders.
- D.
Both gratings produce the same separation between orders, but the orders are better defined with the 4-slit grating.
Correct Answer
D. Both gratings produce the same separation between orders, but the orders are better defined with the 4-slit grating.Explanation
The number of slits in a diffraction grating does not affect the separation between orders. The separation between orders is determined by the slit separation, which is the same for both gratings. However, the orders are better defined with the 4-slit grating because it produces a sharper and more distinct pattern due to the interference of light from multiple slits.Rate this question:
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- 35.
The colors on an oil slick are caused by reflection and
- A.
Diffraction.
- B.
Interference.
- C.
Refraction.
- D.
Polarization.
Correct Answer
B. Interference.Explanation
The colors on an oil slick are caused by interference. When light waves reflect off the oil slick, they interfere with each other, resulting in the formation of different colors. This interference occurs due to the interaction between the incident light waves and the reflected waves, causing constructive or destructive interference depending on their phase relationship. The varying thickness of the oil slick creates a range of path differences for the reflected waves, leading to the interference pattern and the colorful appearance of the oil slick.Rate this question:
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- 36.
We have seen that two monochromatic light waves can interfere constructively or destructively, depending on their phase difference. One consequence of this phenomenon is
- A.
The colors you see when white light is reflected from a soap bubble.
- B.
The appearance of a mirage in the desert.
- C.
A rainbow.
- D.
The way in which Polaroid sunglasses work.
- E.
The formation of an image by a converging lens, such as the lens in your eye.
Correct Answer
A. The colors you see when white light is reflected from a soap bubble.Explanation
When white light is reflected from a soap bubble, it undergoes interference. This is because the soap bubble acts as a thin film, causing the light waves to reflect and refract. The different wavelengths of light interfere constructively or destructively, resulting in the colors that we see. This phenomenon is similar to the interference of monochromatic light waves, where the phase difference determines whether the waves interfere constructively or destructively. Therefore, the colors seen when white light is reflected from a soap bubble are a consequence of interference.Rate this question:
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- 37.
When a beam of light, which is traveling in glass, strikes an air boundary, there is
- A.
A 90° phase change in the reflected beam.
- B.
No phase change in the reflected beam.
- C.
A 180° phase change in the reflected beam.
- D.
A 45° phase change in the reflected beam.
Correct Answer
B. No phase change in the reflected beam.Explanation
When a beam of light traveling in glass strikes an air boundary, there is no phase change in the reflected beam. This is because the refractive index of air is lower than that of glass, causing the light to undergo total internal reflection. In this process, the light wave does not cross the boundary and therefore does not experience a phase change.Rate this question:
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- 38.
When a beam of light, which is traveling in air, is reflected by a glass surface, there is
- A.
A 90° phase change in the reflected beam.
- B.
No phase change in the reflected beam.
- C.
A 180° phase change in the reflected beam.
- D.
A 45° phase change in the reflected beam.
Correct Answer
C. A 180° phase change in the reflected beam.Explanation
When a beam of light is reflected by a glass surface, there is a 180° phase change in the reflected beam. This means that the reflected beam undergoes a shift of half a wavelength compared to the incident beam. This phase change is a result of the change in the refractive index between air and glass, causing the light wave to invert upon reflection.Rate this question:
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- 39.
A soap film is being viewed in white light. As the film becomes very much thinner than the wavelength of blue light, the film
- A.
Appears totally transparent because it reflects no visible light.
- B.
Appears white because it reflects all wavelengths of visible light.
- C.
Appears blue since all other colors are transmitted.
- D.
Appears red since all other colors are transmitted.
Correct Answer
A. Appears totally transparent because it reflects no visible light.Explanation
When a soap film becomes very thin compared to the wavelength of blue light, it acts as a thin layer that is not thick enough to cause interference and reflection of light. Instead, the light passes through the film without being reflected or absorbed, resulting in the film appearing transparent. This is because the film is not able to interact with the blue light in a way that causes it to reflect or scatter, making it appear as if no visible light is being reflected.Rate this question:
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- 40.
In terms of the wavelength of light in magnesium fluoride, what is the minimum thickness of magnesium fluoride coating that must be applied to a glass lens to make it non-reflecting for that wavelength? (The index of refraction of magnesium fluoride is intermediate to that of glass and air.)
- A.
One-fourth wavelength
- B.
One-half wavelength
- C.
One wavelength
- D.
There is no minimum thickness.
Correct Answer
A. One-fourth wavelengthExplanation
The minimum thickness of the magnesium fluoride coating must be one-fourth of the wavelength of light in order to make the glass lens non-reflecting. This is because when light passes through a medium with a different refractive index, some of the light is reflected at the interface between the two mediums. By applying a coating with a thickness equal to one-fourth of the wavelength, the reflected waves from the front and back surfaces of the coating will interfere destructively, resulting in minimal reflection. This phenomenon is known as anti-reflection coating.Rate this question:
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- 41.
A convex lens is placed on a flat glass plate and illuminated from above with monochromatic red light. When viewed from above, concentric bands of red and dark are observed. What does one observe at the exact center of the lens where the lens and the glass plate are in direct contact?
- A.
A bright red spot
- B.
A dark spot
- C.
A rainbow of color
- D.
A bright spot that is some color other than red
Correct Answer
B. A dark spotExplanation
When a convex lens is placed on a flat glass plate and illuminated with monochromatic red light, concentric bands of red and dark are observed. This is due to the phenomenon of interference caused by the interaction of the light waves reflected from both surfaces of the lens and the glass plate. At the exact center of the lens where the lens and the glass plate are in direct contact, there is no air gap for the light waves to interfere with each other. As a result, no interference occurs and no light is reflected or transmitted, leading to the observation of a dark spot.Rate this question:
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- 42.
What principle is responsible for the fact that certain sunglasses can reduce glare from reflected surfaces?
- A.
Refraction
- B.
Polarization
- C.
Diffraction
- D.
Total internal reflection
Correct Answer
B. PolarizationExplanation
Polarization is responsible for reducing glare from reflected surfaces in certain sunglasses. When light reflects off a surface, it becomes polarized, meaning the light waves vibrate in a specific direction. Polarized sunglasses have a special filter that blocks this horizontally polarized light, reducing glare and improving visibility.Rate this question:
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- 43.
For a beam of light, the direction of polarization is defined as
- A.
The beam's direction of travel.
- B.
The direction of the electric field's vibration.
- C.
The direction of the magnetic field's vibration.
- D.
The direction that is mutually perpendicular to the electric and magnetic field vectors.
Correct Answer
B. The direction of the electric field's vibration.Explanation
The direction of polarization for a beam of light is defined as the direction of the electric field's vibration. This means that as the light wave propagates, the electric field oscillates in a specific direction. The direction of polarization is perpendicular to the direction of travel of the light and is determined by the orientation of the electric field vector. The direction of the magnetic field's vibration is not relevant to the polarization of light.Rate this question:
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- 44.
What is the process to obtain polarized light in a dichroic material like a Polaroid film?
- A.
Reflection
- B.
Refraction
- C.
Selective absorption
- D.
Scattering
Correct Answer
C. Selective absorptionExplanation
Polarized light can be obtained in a dichroic material like a Polaroid film through the process of selective absorption. This means that the material selectively absorbs light waves that are oscillating in one particular direction, while allowing light waves oscillating in other directions to pass through. This selective absorption results in the polarization of the transmitted light, as only waves oscillating in a specific direction are able to pass through the material.Rate this question:
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- 45.
When the transmission axes of two Polaroid films are perpendicular to each other, what is the percentage of the incident light which will pass the two films?
- A.
0%
- B.
25%
- C.
50%
- D.
75%
Correct Answer
A. 0%Explanation
When the transmission axes of two Polaroid films are perpendicular to each other, no light can pass through both films. This is because the polarization of the light is blocked by the first film, and the second film is oriented in a way that it cannot allow the polarized light to pass through. Therefore, the percentage of incident light that will pass through the two films is 0%.Rate this question:
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- 46.
Sunlight reflected from the surface of a lake
- A.
Is unpolarized.
- B.
Tends to be polarized with its electric field vector parallel to the surface of the lake.
- C.
Tends to be polarized with its electric field vector perpendicular to the surface of the lake.
- D.
Has undergone refraction by the surface of the lake.
- E.
None of the given answers
Correct Answer
B. Tends to be polarized with its electric field vector parallel to the surface of the lake.Explanation
Sunlight reflected from the surface of a lake tends to be polarized with its electric field vector parallel to the surface of the lake. This is because when light reflects off a non-metallic surface, such as water, it becomes partially polarized. The electric field of the light waves aligns itself with the plane of reflection, which in this case is parallel to the surface of the lake. Therefore, the reflected light tends to be polarized with its electric field vector parallel to the surface of the lake.Rate this question:
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- 47.
The polarization of sunlight is greatest at
- A.
Sunrise.
- B.
Sunset.
- C.
Both sunrise and sunset.
- D.
Midday.
Correct Answer
C. Both sunrise and sunset.Explanation
The polarization of sunlight is greatest at both sunrise and sunset because the sun is closer to the horizon during these times. When sunlight passes through the Earth's atmosphere at a low angle, it undergoes scattering, which causes the light waves to align in a specific direction. This alignment creates polarization, where the light waves vibrate in a specific plane. Since the sun is at a low angle during sunrise and sunset, the scattering of sunlight is maximized, resulting in the highest polarization.Rate this question:
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- 48.
In which of the following is diffraction NOT exhibited?
- A.
Viewing a light source through a small pinhole
- B.
Examining a crystal by X-rays
- C.
Using a microscope under maximum magnification
- D.
Resolving two nearby stars with a telescope
- E.
Determining the direction of polarization with a birefringent crystal
Correct Answer
E. Determining the direction of polarization with a birefringent crystalExplanation
Diffraction is the bending or spreading of waves around obstacles or openings. In all the other options, there is a presence of waves and obstacles that cause diffraction. However, determining the direction of polarization with a birefringent crystal does not involve the bending or spreading of waves. Instead, it relies on the unique properties of birefringent materials to determine the direction of polarization. Therefore, diffraction is not exhibited in this scenario.Rate this question:
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- 49.
On a clear day, the sky appears to be more blue toward the zenith (overhead) than it does toward the horizon. This occurs because
- A.
The atmosphere is denser higher up than it is at the Earth's surface.
- B.
The temperature of the upper atmosphere is higher than it is at the Earth's surface.
- C.
The sunlight travels over a longer path at the horizon, resulting in more scattering.
- D.
None of the given answers
Correct Answer
C. The sunlight travels over a longer path at the horizon, resulting in more scattering.Explanation
The correct answer is that the sunlight travels over a longer path at the horizon, resulting in more scattering. This is because when sunlight enters the Earth's atmosphere, it interacts with the molecules in the air, causing it to scatter. The shorter wavelengths of light, such as blue and violet, scatter more easily than longer wavelengths, such as red and orange. When the sun is directly overhead, the sunlight has a shorter path to travel through the atmosphere, so there is less scattering and the sky appears more blue. However, when the sun is closer to the horizon, the sunlight has to pass through a larger portion of the atmosphere, resulting in more scattering and a less intense blue color.Rate this question:
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- 50.
A beam of light (f = 5.0 * 10^14 Hz) enters a piece of glass (n = 1.5). What is the frequency of the light while it is in the glass?
- A.
5.0 * 10^14 Hz
- B.
7.5 * 10^14 Hz
- C.
3.3 * 10^14 Hz
- D.
None of the given answers
Correct Answer
A. 5.0 * 10^14 HzExplanation
When light enters a medium like glass, its frequency remains unchanged. The frequency of the light while it is in the glass is still 5.0 * 10^14 Hz.Rate this question:
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