Chapter 33: Interference and Diffraction

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# Chapter 33: Interference and Diffraction - PowerPoint PPT Presentation

Chapter 33: Interference and Diffraction. Section 33-1: Phase Difference and Coherence. A phase shift of 180º occurs when a light wave . is transmitted through a boundary surface into a medium that is more dense than the medium from which the wave came.

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### Chapter 33: Interferenceand Diffraction

Section 33-1: Phase Difference and Coherence

A phase shift of 180º occurs when a light wave
• is transmitted through a boundary surface into a medium that is more dense than the medium from which the wave came.
• is transmitted through a boundary surface into a medium that is less dense than the medium from which the wave came.
• reflects from the boundary surface of a medium that is less dense than the medium in which the wave is traveling.
• reflects from the boundary surface of a medium that is more dense than the medium in which the wave is traveling.
• Both c and d are correct.
A phase shift of 180º occurs when a light wave
• is transmitted through a boundary surface into a medium that is more dense than the medium from which the wave came.
• is transmitted through a boundary surface into a medium that is less dense than the medium from which the wave came.
• reflects from the boundary surface of a medium that is less dense than the medium in which the wave is traveling.
• reflects from the boundary surface of a medium that is more dense than the medium in which the wave is traveling.
• Both c and d are correct.
Which, if any, of the following conditions is not necessary for the light waves from two sources to be coherent?
• They must have the same frequency.
• They must have the same amplitude.
• They must have the same wavelength.
• They must have a constant phase difference.
• All of these conditions are necessary.
Which, if any, of the following conditions is not necessary for the light waves from two sources to be coherent?
• They must have the same frequency.
• They must have the same amplitude.
• They must have the same wavelength.
• They must have a constant phase difference.
• All of these conditions are necessary.
Diffraction of sound waves is more readily observable than that of light waves because
• sound waves are longitudinal and not transverse.
• sound waves have a higher frequency than light waves.
• sound waves have a lower velocity than light waves.
• sound waves have longer wavelengths than do light waves.
• sound waves occur in air and light waves do not.
Diffraction of sound waves is more readily observable than that of light waves because
• sound waves are longitudinal and not transverse.
• sound waves have a higher frequency than light waves.
• sound waves have a lower velocity than light waves.
• sound waves have longer wavelengths than do light waves.
• sound waves occur in air and light waves do not.

In the figure, a beam of light from an underwater source is incident on a layer of carbon disulfide and the glass bottom of the container. The container is surrounded by air. Some of the refracted and reflected rays are shown in the diagram. For the rays shown, the interface at which the reflected light changes phase is

• 1 only
• 2 only
• 3 only
• 1 and 2
• 2 and 3

In the figure, a beam of light from an underwater source is incident on a layer of carbon disulfide and the glass bottom of the container. The container is surrounded by air. Some of the refracted and reflected rays are shown in the diagram. For the rays shown, the interface at which the reflected light changes phase is

• 1 only
• 2 only
• 3 only
• 1 and 2
• 2 and 3
The two waves shown come from a source where they were initially coherent. The path difference could be
• ⅓ λ
• ½ λ
• ¼ λ
• λ
• It is not possible to answer this question without additional information.
The two waves shown come from a source where they were initially coherent. The path difference could be
• ⅓ λ
• ½ λ
• ¼ λ
• λ
• It is not possible to answer this question without additional information.
• π
• 2π/3
• π/2
• It is not possible to answer this question without additional information.
• π
• 2π/3
• π/2
• It is not possible to answer this question without additional information.
Which of the following statements is true?
• When two harmonic waves of the same frequency and wavelength but differing in phase combine, the resultant wave is a harmonic wave whose amplitude depends on the phase difference.
• A phase difference between two waves can be the result of a difference in path length.
• A path difference of one wavelength is equivalent to no phase difference at all.
• A phase difference between two waves can be the result of reflection from a boundary surface.
• All of these are correct.
Which of the following statements is true?
• When two harmonic waves of the same frequency and wavelength but differing in phase combine, the resultant wave is a harmonic wave whose amplitude depends on the phase difference.
• A phase difference between two waves can be the result of a difference in path length.
• A path difference of one wavelength is equivalent to no phase difference at all.
• A phase difference between two waves can be the result of reflection from a boundary surface.
• All of these are correct.

### Chapter 33: Interferenceand Diffraction

Section 33-2: Interference in Thin Films

For us to see interference phenomena in a thin film,
• the incoming light must be monochromatic.
• the index of refraction of the thin film must be greater than the index of refraction of the material below it.
• the index of refraction of the thin film must be less than the index of refraction of the material below it.
• the incoming light must be multicolored.
• None of these conditions need exist.
For us to see interference phenomena in a thin film,
• the incoming light must be monochromatic.
• the index of refraction of the thin film must be greater than the index of refraction of the material below it.
• the index of refraction of the thin film must be less than the index of refraction of the material below it.
• the incoming light must be multicolored.
• None of these conditions need exist.
Why are fringes not observed if the angle of the wedge of air in the diagram is too large?
• For a large angle, the small-angle approximation (sin θ≈θ) is not valid.
• The light passing through the wedge of air loses its coherence.
• The fringes overlap.
• The fringes are too close together to be seen individually.
• None of these is correct.
Why are fringes not observed if the angle of the wedge of air in the diagram is too large?
• For a large angle, the small-angle approximation (sin θ≈θ) is not valid.
• The light passing through the wedge of air loses its coherence.
• The fringes overlap.
• The fringes are too close together to be seen individually.
• None of these is correct.
For two identical rays of light to interfere destructively, their path lengths
• must be equal.
• must differ by an odd number of half wavelengths.
• must differ by an integral number of wavelengths.
For two identical rays of light to interfere destructively, their path lengths
• must be equal.
• must differ by an odd number of half wavelengths.
• must differ by an integral number of wavelengths.
The main effect contributing to the production of different colors seen on a soap bubble is
• the dispersion of light by the water in the soap.
• the interference of light reflected from the front and back of the soap film.
• the polarization of light by the soap film.
• total internal reflection of light in the soap film.
• None of the statements is correct.
The main effect contributing to the production of different colors seen on a soap bubble is
• the dispersion of light by the water in the soap.
• the interference of light reflected from the front and back of the soap film.
• the polarization of light by the soap film.
• total internal reflection of light in the soap film.
• None of the statements is correct.

A wedge-shaped film of air is formed by placing two flat glass plates with one end touching each other and the other end spaced by a gold leaf. The wedge is then illuminated using a monochromatic light of wavelength 590 nm from above and the complete fringe pattern is shown. The thickness of the gold leaf is approximately

• 7.1 m
• 7.4 m
• 6.5 m
• 6.8 m
• 7.8 m

A wedge-shaped film of air is formed by placing two flat glass plates with one end touching each other and the other end spaced by a gold leaf. The wedge is then illuminated using a monochromatic light of wavelength 590 nm from above and the complete fringe pattern is shown. The thickness of the gold leaf is approximately

• 7.1 m
• 7.4 m
• 6.5 m
• 6.8 m
• 7.8 m

A wedge-shaped film of air is formed by placing a glass plate of unknown flatness upon second glass plate that is known to be perfectly flat. The wedge is then illuminated using a monochromatic light from above and a fringe pattern is shown. The wedge of air is thicker on the right than on the left. From the fringe pattern one can conclude that the bottom surface of the first glass plate is

• perfectly flat.
• concave.
• convex.
• No conclusion can be drawn about the shape.

A wedge-shaped film of air is formed by placing a glass plate of unknown flatness upon second glass plate that is known to be perfectly flat. The wedge is then illuminated using a monochromatic light from above and a fringe pattern is shown. The wedge of air is thicker on the right than on the left. From the fringe pattern one can conclude that the bottom surface of the first glass plate is

• perfectly flat.
• concave.
• convex.
• No conclusion can be drawn about the shape.

The interference pattern is from a lens placed on a flat reflecting surface illuminate using a monochromatic light from above. From the pattern one can conclude that the lens

• is more curved on the left and right sides compared to top and bottom.
• is more curved on the top and bottom compared to the left and right sides.
• has a spherical surface.
• has a concave surface.
• None of the above statements is correct.

The interference pattern is from a lens placed on a flat reflecting surface illuminate using a monochromatic light from above. From the pattern one can conclude that the lens

• is more curved on the left and right sides compared to top and bottom.
• is more curved on the top and bottom compared to the left and right sides.
• has a spherical surface.
• has a concave surface.
• None of the above statements is correct.

### Chapter 33: Interferenceand Diffraction

Section 33-3: Two-Slit Interference Pattern and Concept Check 33-1

Two narrow slits are illuminated by monochromatic light. If the distance between the slits is equal to 2.75 wavelengths, what is the maximum number of dark fringes that can be seen on a screen?

• 2
• 3
• 4
• 5
• 6

Two narrow slits are illuminated by monochromatic light. If the distance between the slits is equal to 2.75 wavelengths, what is the maximum number of dark fringes that can be seen on a screen?

• 2
• 3
• 4
• 5
• 6
Which of the following statements about Young's double-slit experiment is false?
• The bands of light are caused by the interference of the light coming from the two slits.
• The results of the double-slit experiment support the particle theory of light.
• Double-slit interference patterns can also be produced with sound and water waves.
• If the slits are moved closer together, the bands of light on the screen are spread farther apart.
• The pattern of light on the screen consists of many bands, not just two bands.
Which of the following statements about Young's double-slit experiment is false?
• The bands of light are caused by the interference of the light coming from the two slits.
• The results of the double-slit experiment support the particle theory of light.
• Double-slit interference patterns can also be produced with sound and water waves.
• If the slits are moved closer together, the bands of light on the screen are spread farther apart.
• The pattern of light on the screen consists of many bands, not just two bands.

The distance between the slits in a double-slit experiment is increased by a factor of 4. If the distance between the fringes is small compared with the distance from the slits to the screen, the distance between adjacent fringes near the center of the interference pattern

• increases by a factor of 2.
• increases by a factor of 4.
• depends on the width of the slits.
• decreases by a factor of 2.
• decreases by a factor of 4.

The distance between the slits in a double-slit experiment is increased by a factor of 4. If the distance between the fringes is small compared with the distance from the slits to the screen, the distance between adjacent fringes near the center of the interference pattern

• increases by a factor of 2.
• increases by a factor of 4.
• depends on the width of the slits.
• decreases by a factor of 2.
• decreases by a factor of 4.

In a double-slit experiment, the distance from the slits to the screen is decreased by a factor of 2. If the distance between the fringes is small compared with the distance from the slits to the screen, the distance between adjacent fringes

• increases by a factor of 2.
• increases by a factor of 4.
• depends on the width of the slits.
• decreases by a factor of 2.
• decreases by a factor of 4.

In a double-slit experiment, the distance from the slits to the screen is decreased by a factor of 2. If the distance between the fringes is small compared with the distance from the slits to the screen, the distance between adjacent fringes

• increases by a factor of 2.
• increases by a factor of 4.
• depends on the width of the slits.
• decreases by a factor of 2.
• decreases by a factor of 4.

In order to produce several easily visible interference fringes from two narrow slits using light of a single wavelength, the distance between the slits must be of the order

• of a few tenths of the wavelength.
• of a few wavelengths.
• of a few tens wavelengths.
• of a few hundreds wavelengths.
• The distance does not matter.

In order to produce several easily visible interference fringes from two narrow slits using light of a single wavelength, the distance between the slits must be of the order

• of a few tenths of the wavelength.
• of a few wavelengths.
• of a few tens wavelengths.
• of a few hundreds wavelengths.
• The distance does not matter.
When the slits in Young’s experiment are moved closer together, the fringes
• remains unchanged.
• move closer together.
• move further apart.
When the slits in Young’s experiment are moved closer together, the fringes
• remains unchanged.
• move closer together.
• move further apart.

A narrow, horizontal slit is 0.50 mm above a horizontal plane mirror. The slit is illuminated by light of wavelength 400 nm. The interference pattern is viewed on a screen 10.0 m from the slit. What is the vertical distance from the mirror to the first bright line?

• 1.0 mm
• 2.0 mm
• 3.0 mm
• 4.0 mm
• 1.2 mm

A narrow, horizontal slit is 0.50 mm above a horizontal plane mirror. The slit is illuminated by light of wavelength 400 nm. The interference pattern is viewed on a screen 10.0 m from the slit. What is the vertical distance from the mirror to the first bright line?

• 1.0 mm
• 2.0 mm
• 3.0 mm
• 4.0 mm
• 1.2 mm

### Chapter 33: Interferenceand Diffraction

Section 33-4: Diffraction Pattern of a Single Slit

• the narrower the slit, the narrower the central diffraction maximum.
• the narrower the slit, the wider the central diffraction maximum.
• the width of the central diffraction maximum is independent of the width of the slit.
• the narrower the slit, the narrower the central diffraction maximum.
• the narrower the slit, the wider the central diffraction maximum.
• the width of the central diffraction maximum is independent of the width of the slit.

The graphs are plots of relative intensities of various diffraction patterns versus the sine of the angle from the central maximum. Which graph represents the diffraction pattern from the widest single slit?

The graphs are plots of relative intensities of various diffraction patterns versus the sine of the angle from the central maximum. Which graph represents the diffraction pattern from the widest single slit?

The bending of light around an obstacle such as the edge of a slit is called
• diffraction
• dispersion
• reflection
• refraction
• polarization
The bending of light around an obstacle such as the edge of a slit is called
• diffraction
• dispersion
• reflection
• refraction
• polarization

The diffraction pattern of a single slit is shown in the figure. At which point is the path difference of the extreme rays approximately two wavelengths?

The diffraction pattern of a single slit is shown in the figure. At which point is the path difference of the extreme rays approximately two wavelengths?

As the width of the slit producing a single-slit diffraction pattern is slowly and steadily reduced (always remaining larger than the wavelength of the light), the diffraction pattern

• slowly and steadily gets wider.
• slowly and steadily gets brighter.
• does not change because the wavelength of the light does not change.
• slowly and steadily gets narrower.
• None of these is correct.

As the width of the slit producing a single-slit diffraction pattern is slowly and steadily reduced (always remaining larger than the wavelength of the light), the diffraction pattern

• slowly and steadily gets wider.
• slowly and steadily gets brighter.
• does not change because the wavelength of the light does not change.
• slowly and steadily gets narrower.
• None of these is correct.
The pattern of light and dark fringes formed in Young's double-slit experiment is due to
• interference and dispersion.
• diffraction and refraction.
• refraction and interference.
• refraction and dispersion.
• interference and diffraction.
The pattern of light and dark fringes formed in Young's double-slit experiment is due to
• interference and dispersion.
• diffraction and refraction.
• refraction and interference.
• refraction and dispersion.
• interference and diffraction.

The interference and diffraction envelopes of a double slit are shown separately but to the same scale in the figure. For this arrangement, the number of fringes in one of the second diffraction maxima is

• 3
• 4
• 5
• 7
• 0

The interference and diffraction envelopes of a double slit are shown separately but to the same scale in the figure. For this arrangement, the number of fringes in one of the second diffraction maxima is

• 3
• 4
• 5
• 7
• 0
The fringes shown are the result of
• a single slit.
• a double slit.
• three slits.
• five slits.
• many slits.
The fringes shown are the result of
• a single slit.
• a double slit.
• three slits.
• five slits.
• many slits.

### Chapter 33: Interferenceand Diffraction

Section 33-5: Using Phasors to Add Harmonic Waves

Which of the phasor diagrams shows the first minimum for five equally spaced in-phase sources?
Which of the phasor diagrams shows the first minimum for five equally spaced in-phase sources?

Five coherent sources are used to produce an interference pattern. The phasor diagram shown could be used to calculate the intensity of the

• first minimum in the interference pattern.
• second maximum in an interference pattern.
• first maximum in an interference pattern.
• second minimum in an interference pattern.
• None of these is correct.

Five coherent sources are used to produce an interference pattern. The phasor diagram shown could be used to calculate the intensity of the

• first minimum in the interference pattern.
• second maximum in an interference pattern.
• first maximum in an interference pattern.
• second minimum in an interference pattern.
• None of these is correct.

### Chapter 33: Interferenceand Diffraction

Section 33-6: Fraunhofer and Fresnel Diffraction

In demonstrating single-slit Fraunhofer diffraction, decreasing the wavelength of the light while keeping the slit width constant
• does not affect the width of the central maximum.
• increases the number of fringes within the central maximum.
• decreases the number of fringes within the central maximum.
• increases the width of the central maximum.
• decreases the width of the central maximum
In demonstrating single-slit Fraunhofer diffraction, decreasing the wavelength of the light while keeping the slit width constant
• does not affect the width of the central maximum.
• increases the number of fringes within the central maximum.
• decreases the number of fringes within the central maximum.
• increases the width of the central maximum.
• decreases the width of the central maximum

### Chapter 33: Interferenceand Diffraction

Section 33-7: Diffraction and Resolution and Concept Check 33-2

Rayleigh's criterion is most closely associated with
• diffraction
• coherence
• dispersion
• polarization
• reflection
Rayleigh's criterion is most closely associated with
• diffraction
• coherence
• dispersion
• polarization
• reflection

The pupil of the human eye has a diameter of about 5 mm. When the wavelength of light incident on the pupil is 500 nm, the smallest angular separation of two resolvable sources is approximately

• 1"
• 1'
• 10º

The pupil of the human eye has a diameter of about 5 mm. When the wavelength of light incident on the pupil is 500 nm, the smallest angular separation of two resolvable sources is approximately

• 1"
• 1'
• 10º

The white circles in the figure represent minima of the diffraction pattern formed when a bright point-source object is viewed through a small circular opening. In accordance with Rayleigh's criterion, the closest central maximum of another point source that could lie in this pattern and still be barely resolvable

• would be at point A.
• would be at point B.
• would be at point C.
• would be at point D.
• must lie outside all discernible diffraction rings.

The white circles in the figure represent minima of the diffraction pattern formed when a bright point-source object is viewed through a small circular opening. In accordance with Rayleigh's criterion, the closest central maximum of another point source that could lie in this pattern and still be barely resolvable

• would be at point A.
• would be at point B.
• would be at point C.
• would be at point D.
• must lie outside all discernible diffraction rings.

The diffraction image of the point object O is indicated in the figure. Of the point objects A, B, C, D, and E, which is the one closest to O and whose diffraction image could just be resolved from that of O according to the Rayleigh criterion?

The diffraction image of the point object O is indicated in the figure. Of the point objects A, B, C, D, and E, which is the one closest to O and whose diffraction image could just be resolved from that of O according to the Rayleigh criterion?

Diffraction occurs when light passes
• by a small particle.
• through a small hole.
• through a double slit.
• by a sharp edge.
• Diffraction occurs in all of these conditions.
Diffraction occurs when light passes
• by a small particle.
• through a small hole.
• through a double slit.
• by a sharp edge.
• Diffraction occurs in all of these conditions.

The size of the smallest things that can be seen with an optical microscope is limited by diffraction. Which of the following could help a microscopist see smaller things?

• A more powerful microscope could be used.
• The microscope could have a lens with a shorter focal length.
• The microscope could have a lens with a longer focal length.
• The diameter of the lens could be smaller.
• Light with a shorter wavelength could be used.

The size of the smallest things that can be seen with an optical microscope is limited by diffraction. Which of the following could help a microscopist see smaller things?

• A more powerful microscope could be used.
• The microscope could have a lens with a shorter focal length.
• The microscope could have a lens with a longer focal length.
• The diameter of the lens could be smaller.
• Light with a shorter wavelength could be used.

An antenna for receiving television signals from a satellite has a diameter of 3 m. The signals have a wavelength of 24 cm. If the diameter of the antenna is reduced to 50 cm, for what signal wavelengths does the antenna still have the same angular resolution?

• 4.0 cm
• 6.0 cm
• 8.0 cm
• 1.4 m
• 24 cm

An antenna for receiving television signals from a satellite has a diameter of 3 m. The signals have a wavelength of 24 cm. If the diameter of the antenna is reduced to 50 cm, for what signal wavelengths does the antenna still have the same angular resolution?

• 4.0 cm
• 6.0 cm
• 8.0 cm
• 1.4 m
• 24 cm
In accordance with the Rayleigh criterion, two points can be just resolved if the centers of their diffraction patterns are separated by
• one wavelength.
• twice the width of either central maximum.
• one-half the width of either central maximum.
• the width of the aperture.
• the reciprocal of one wavelength.
In accordance with the Rayleigh criterion, two points can be just resolved if the centers of their diffraction patterns are separated by
• one wavelength.
• twice the width of either central maximum.
• one-half the width of either central maximum.
• the width of the aperture.
• the reciprocal of one wavelength.

### Chapter 33: Interferenceand Diffraction

Section 33-8: Diffraction Gratings

The type of electromagnetic radiation that is employed when crystals are used as diffraction gratings is
• infrared
• X-rays
• visible
• ultraviolet
• microwaves
The type of electromagnetic radiation that is employed when crystals are used as diffraction gratings is
• infrared
• X-rays
• visible
• ultraviolet
• microwaves

Monochromatic light of wavelength l is normally incident on a plane diffraction grating, and three rays of light (A, B, and C) are observed. Of these three rays

• A is the first order, B is the second order, and C is the third order.
• B is the first order, and A and C are the second order.
• A is the zero order, B is the first order, and C is the second order.
• B is the zero order, and A and C are the first order.
• A, B, and C are all the first order.

Monochromatic light of wavelength l is normally incident on a plane diffraction grating, and three rays of light (A, B, and C) are observed. Of these three rays

• A is the first order, B is the second order, and C is the third order.
• B is the first order, and A and C are the second order.
• A is the zero order, B is the first order, and C is the second order.
• B is the zero order, and A and C are the first order.
• A, B, and C are all the first order.

A student looks through a transmission grating at the light from a helium light source. He sees the red, yellow, and green light from the source superimposed on a meterstick. If the yellow lines are the ones indicated in the figure, then

• 1 and 2 are green; 3 and 4 are red.
• 1 and 4 are red; 2 and 3 are green.
• 1 and 4 are green; 2 and 3 are red.
• 1 and 3 are red; 2 and 4 are green.
• 1 and 3 are green; 2 and 4 are red.

A student looks through a transmission grating at the light from a helium light source. He sees the red, yellow, and green light from the source superimposed on a meterstick. If the yellow lines are the ones indicated in the figure, then

• 1 and 2 are green; 3 and 4 are red.
• 1 and 4 are red; 2 and 3 are green.
• 1 and 4 are green; 2 and 3 are red.
• 1 and 3 are red; 2 and 4 are green.
• 1 and 3 are green; 2 and 4 are red.
If the prism spectrum of a source is a line spectrum, the grating spectrum would
• be an absorption spectrum.
• also be a line spectrum.
• be a continuous spectrum.
If the prism spectrum of a source is a line spectrum, the grating spectrum would
• be an absorption spectrum.
• also be a line spectrum.
• be a continuous spectrum.

White light is in one case dispersed by refraction on passing through a glass prism and in a second case diffracted by means of a grating. When the red component and the blue component are considered, it is found that

• red is both refracted and diffracted at greater angles than blue.
• blue is both refracted and diffracted at greater angles than red.
• red is refracted at a greater angle than blue, but blue is diffracted at a greater angle than red.
• blue is refracted at a greater angle than red, but red is diffracted at a greater angle than blue.
• both red and blue are refracted at the same angle and diffracted at the same angle.

White light is in one case dispersed by refraction on passing through a glass prism and in a second case diffracted by means of a grating. When the red component and the blue component are considered, it is found that

• red is both refracted and diffracted at greater angles than blue.
• blue is both refracted and diffracted at greater angles than red.
• red is refracted at a greater angle than blue, but blue is diffracted at a greater angle than red.
• blue is refracted at a greater angle than red, but red is diffracted at a greater angle than blue.
• both red and blue are refracted at the same angle and diffracted at the same angle.

Which of two diffraction gratings, one with N1 slits per centimeter and the other with N2 slits per centimeter, has the greater resolving power if N1 is greater than N2?

• the grating with N1 slits per centimeter
• the grating with N2 slits per centimeter
• They both have the same resolving power, but the one with N1 slits per centimeter has sharper spectral lines.
• They both have the same resolving power, but the one with N2 slits per centimeter has sharper spectral lines.
• The width of the individual slits must be known to answer this question.

Which of two diffraction gratings, one with N1 slits per centimeter and the other with N2 slits per centimeter, has the greater resolving power if N1 is greater than N2?

• the grating with N1 slits per centimeter
• the grating with N2 slits per centimeter
• They both have the same resolving power, but the one with N1 slits per centimeter has sharper spectral lines.
• They both have the same resolving power, but the one with N2 slits per centimeter has sharper spectral lines.
• The width of the individual slits must be known to answer this question.

The spacing between the adjacent lines of a diffraction grating is the same as the distance between the two slits in the Young’s double slit experiment. Both are illuminated by light of the same wavelength. In which way do the interference fringes seen on the screen differ for the two methods?

• There is no difference in the interference fringes.
• The fringes from the grating are farther apart.
• The fringes from the double slit are farther apart.
• Each of the fringes from the grating is narrower than the double slit.
• Each of the fringes from the double slit is narrower than the grating.

The spacing between the adjacent lines of a diffraction grating is the same as the distance between the two slits in the Young’s double slit experiment. Both are illuminated by light of the same wavelength. In which way do the interference fringes seen on the screen differ for the two methods?

• There is no difference in the interference fringes.
• The fringes from the grating are farther apart.
• The fringes from the double slit are farther apart.
• Each of the fringes from the grating is narrower than the double slit.
• Each of the fringes from the double slit is narrower than the grating.