Question 1

Consider an experiment where we send monochromatic light to a distant screen through a single narrow slit. The distance between adjacent dark fringes in the diffraction pattern displayed on the screen
-We look at fringes farther from the central maximum.

Accepted Answer

The distance between adjacent dark fringes in a diffraction pattern increases as we look at fringes farther from the central maximum. This is because the diffraction pattern spreads out more as the angle from the central maximum increases, leading to wider spacing between the fringes.

Question 2

In the region where their beams overlap, two car headlights will create a clear interference pattern on a distant screen.

Accepted Answer

Car headlights produce incoherent light, meaning the light waves are not synchronized in phase or frequency, which is necessary for creating a clear interference pattern.

Question 3

If we shine white light through two slits onto a distant screen, we will see a clear interference pattern.

Accepted Answer

The answer of If we shine white light through two...

Question 4

Imagine we have an adjustable slit that we can make wider or narrower. If we shine light of a fixed intensity on the slit, and then crank the slit so its width decreases (while keeping other things the same), will the light at the center of the central peak on the display screen?

Accepted Answer

As the slit width decreases, diffraction increases, causing the light to spread out more, which results in a dimmer central peak on the display screen.

Question 5

Eagles and other predatory birds have very sharp eyesight. The pupil of an eagle's eye is roughly twice the size of a human's under similar (daylight) conditions. A friend claims to have read that an eagle's eye has 8 times the resolving power of a human eye in broad daylight. This is physically impossible.

Accepted Answer

The answer of Eagles and other predatory birds have very...

Question 6

With an optically perfect 200-power telescope with a 1.5-inch-diameter tube, you can resolve objects roughly how many times closer together than you could with your naked eye? (Choose the closest answer.)

Accepted Answer

The answer of With an optically perfect 200-power telescope with...

Question 7

Sunlight falling on a spaceship in a vacuum will cause the spaceship to become a bit positively charged.

Accepted Answer

Sunlight consists of photons, and when these photons hit the surface of a spaceship, they can eject electrons from the material due to the photoelectric effect. This loss of electrons leaves the spaceship with a net positive charge.

Question 8

In the apparatus shown in figure Q4.1a, the value displayed by the ammeter is proportional to

Accepted Answer

The answer of In the apparatus shown in figure Q4.1a,...

Question 9

For experiments involving the setup shown in figure Q4.1a, which of the following possible results (if seen) about the value displayed by the ammeter would probably not be consistent with the wave model of light?

Accepted Answer

The answer of For experiments involving the setup shown in...

Question 10

In the apparatus shown in figure Q4.1b, the final value displayed by the voltmeter is proportional to

Accepted Answer

The answer of In the apparatus shown in figure Q4.1b,...

Question 11

For experiments involving the setup shown in figure $\mathrm{Q} 4.1 \mathrm{~b}$, which of the following possible results (if seen) regarding the final value displayed by the voltmeter would probably not be consistent with the wave model of light?

(b) Metallic plate (cathode)

Accepted Answer

The answer of For experiments involving the setup shown in...

Question 12

In experiments involving the setup shown in figure Q4.1b, the value that the voltmeter displays increases for a short period of time after light starts shining on the cathode, but then quickly settles down to a fixed value. Why?

Accepted Answer

The answer of In experiments involving the setup shown in...

Question 13

In an experiment involving the apparatus shown in figure Q4.1b, suppose that after shining light on the cathode long enough that the voltmeter settles down to a fixed value, we suddenly cut off the light. If the voltmeter is truly ideal, what happens to the value displayed?

Accepted Answer

The answer of In an experiment involving the apparatus shown...

Question 14

A beam of light $P$ has twice the wavelength but the same intensity as beam $Q$. The number of photons that hit a given area in a given time when it is illuminated by beam $P$ is (A) twice, (B) the same, or (C) one-half of the number that hit when the area is illuminated by beam $Q$ ?

Accepted Answer

The number of photons is inversely proportional to the wavelength. Since the wavelength of beam P is twice that of beam Q, the number of photons in beam P is one-half that of beam Q.

Question 15

Though this would be tricky to do in practice, suppose we could increase the frequency of light illuminating the cathode of the apparatus shown in figure Q4.1a while holding the intensity of that light constant. What would Einstein's photon model predict would happen to the value displayed by the ammeter as the frequency increases? (Assume that the light's frequency is always above the cathode's cutoff frequency.)

Accepted Answer

The answer of Though this would be tricky to do...

Question 16

The work function $W$ for copper is $4.65 \mathrm{eV}$. Visible light will dislodge electrons from a copper surface.

Accepted Answer

Visible light has photon energies ranging from about 1.65 eV (red) to 3.1 eV (violet), which are below the work function of copper (4.65 eV), meaning visible light does not have enough energy to dislodge electrons from a copper surface.

Question 17

If you want to design a phototube that is able to respond to all visible light wavelengths, what should its cathode's work function be?

Accepted Answer

The work function of the cathode must be below $1.77 \mathrm{eV}$ to respond to all visible light wavelengths, as $1.77 \mathrm{eV}$ corresponds to the energy of the red edge of the visible spectrum (around 700 nm), and lower work function values allow the cathode to be sensitive to even lower energy (longer wavelength) light.

Question 18

If you want to design a phototube that ignores all visible light, what should its cathode's work function be?

Accepted Answer

The visible light spectrum ranges from about 400 nm (violet) to 700 nm (red), corresponding to photon energies from approximately 3.1 eV to 1.77 eV, respectively. To ignore all visible light, the cathode's work function needs to be above the highest energy of visible light, which is above 3.1 eV. This ensures that photons from the visible spectrum do not have enough energy to eject electrons from the cathode.

Question 19

Violet light with a wavelength of $430 \mathrm{~nm}$ falls on a sodium plate $(W=2.75 \mathrm{eV})$ and a potassium plate $(W=$ $2.30 \mathrm{eV})$. Which of of the following statements is true?

Accepted Answer

To determine which plates emit electrons and the kinetic energy of the emitted electrons, we use the photoelectric effect equation: $E_{photon} = W + K.E.$, where $E_{photon}$ is the energy of the incoming photon, $W$ is the work function of the material, and $K.E.$ is the kinetic energy of the emitted electron. The energy of the incoming photon can be calculated using $E_{photon} = \frac{hc}{\lambda}$, where $h$ is Planck's constant ($6.626 \times 10^{-34} \, \text{m}^2 \text{kg} / \text{s}$), $c$ is the speed of light ($3.00 \times 10^8 \, \text{m/s}$), and $\lambda$ is the wavelength of the light ($430 \, \text{nm}$ or $430 \times 10^{-9} \, \text{m}$). First, calculate the energy of the violet light photon:$$E_{photon} = \frac{6.626 \times 10^{-34} \times 3.00 \times 10^8}{430 \times 10^{-9}} = \frac{1.9878 \times 10^{-19}}{430} \approx 4.62 \times 10^{-19} \, \text{J}$$Converting this energy to electron volts (eV) (1 eV = $1.602 \times 10^{-19} \, \text{J}$):$$E_{photon} \approx \frac{4.62 \times 10^{-19}}{1.602 \times 10^{-19}} \approx 2.88 \, \text{eV}$$Since the work function of sodium is $2.75 \, \text{eV}$ and for potassium is $2.30 \, \text{eV}$, the energy of the incoming photon is sufficient to overcome the work function of both metals. Therefore, both plates emit electrons.The kinetic energy of the emitted electrons is the difference between the photon energy and the work function:- For sodium: $K.E._{Na} = 2.88 \, \text{eV} - 2.75 \, \text{eV} = 0.13 \, \text{eV}$- For potassium: $K.E._{K} = 2.88 \, \text{eV} - 2.30 \, \text{eV} = 0.58 \, \text{eV}$Thus, both plates emit electrons, but those emitted by the potassium plate have the larger kinetic energy.

Question 20

A long-wavelength photon, because it is larger, carries more total energy than a short-wavelength photon.

Accepted Answer

The energy of a photon is inversely proportional to its wavelength, meaning a short-wavelength photon carries more energy than a long-wavelength photon.

Quiz 5: Matter Behaves Like Waves Quantum Physics

Consider an experiment where we send monochromatic light to a distant screen through a single narrow slit. The distance between adjacent dark fringes in the diffraction pattern displayed on the screen -We look at fringes farther from the central maximum.

In the region where their beams overlap, two car headlights will create a clear interference pattern on a distant screen.

If we shine white light through two slits onto a distant screen, we will see a clear interference pattern.

Imagine we have an adjustable slit that we can make wider or narrower. If we shine light of a fixed intensity on the slit, and then crank the slit so its width decreases (while keeping other things the same) , will the light at the center of the central peak on the display screen?

With an optically perfect 200-power telescope with a 1.5-inch-diameter tube, you can resolve objects roughly how many times closer together than you could with your naked eye? (Choose the closest answer.)

Sunlight falling on a spaceship in a vacuum will cause the spaceship to become a bit positively charged.

In the apparatus shown in figure Q4.1a, the value displayed by the ammeter is proportional to

For experiments involving the setup shown in figure Q4.1a, which of the following possible results (if seen) about the value displayed by the ammeter would probably not be consistent with the wave model of light?

In the apparatus shown in figure Q4.1b, the final value displayed by the voltmeter is proportional to

In experiments involving the setup shown in figure Q4.1b, the value that the voltmeter displays increases for a short period of time after light starts shining on the cathode, but then quickly settles down to a fixed value. Why?

In an experiment involving the apparatus shown in figure Q4.1b, suppose that after shining light on the cathode long enough that the voltmeter settles down to a fixed value, we suddenly cut off the light. If the voltmeter is truly ideal, what happens to the value displayed?

A beam of light $P$ has twice the wavelength but the same intensity as beam $Q$ . The number of photons that hit a given area in a given time when it is illuminated by beam $P$ is (A) twice, (B) the same, or (C) one-half of the number that hit when the area is illuminated by beam $Q$ ?

The work function $W$ for copper is $4.65 \mathrm{eV}$ . Visible light will dislodge electrons from a copper surface.

If you want to design a phototube that is able to respond to all visible light wavelengths, what should its cathode's work function be?

If you want to design a phototube that ignores all visible light, what should its cathode's work function be?

Violet light with a wavelength of $430 \mathrm{~nm}$ falls on a sodium plate $(W=2.75 \mathrm{eV})$ and a potassium plate $(W=$ $2.30 \mathrm{eV})$ . Which of of the following statements is true?

A long-wavelength photon, because it is larger, carries more total energy than a short-wavelength photon.

Quiz 5: Matter Behaves Like Waves Quantum Physics

Consider an experiment where we send monochromatic light to a distant screen through a single narrow slit. The distance between adjacent dark fringes in the diffraction pattern displayed on the screen -We look at fringes farther from the central maximum.

In the region where their beams overlap, two car headlights will create a clear interference pattern on a distant screen.

If we shine white light through two slits onto a distant screen, we will see a clear interference pattern.

Imagine we have an adjustable slit that we can make wider or narrower. If we shine light of a fixed intensity on the slit, and then crank the slit so its width decreases (while keeping other things the same) , will the light at the center of the central peak on the display screen?

With an optically perfect 200-power telescope with a 1.5-inch-diameter tube, you can resolve objects roughly how many times closer together than you could with your naked eye? (Choose the closest answer.)

Sunlight falling on a spaceship in a vacuum will cause the spaceship to become a bit positively charged.

In the apparatus shown in figure Q4.1a, the value displayed by the ammeter is proportional to

For experiments involving the setup shown in figure Q4.1a, which of the following possible results (if seen) about the value displayed by the ammeter would probably not be consistent with the wave model of light?

In the apparatus shown in figure Q4.1b, the final value displayed by the voltmeter is proportional to

For experiments involving the setup shown in figure Q4.1 b\mathrm{Q} 4.1 \mathrm{~b}Q4.1 b , which of the following possible results (if seen) regarding the final value displayed by the voltmeter would probably not be consistent with the wave model of light? (b) Metallic plate (cathode)

In experiments involving the setup shown in figure Q4.1b, the value that the voltmeter displays increases for a short period of time after light starts shining on the cathode, but then quickly settles down to a fixed value. Why?

In an experiment involving the apparatus shown in figure Q4.1b, suppose that after shining light on the cathode long enough that the voltmeter settles down to a fixed value, we suddenly cut off the light. If the voltmeter is truly ideal, what happens to the value displayed?

A beam of light PPP has twice the wavelength but the same intensity as beam QQQ . The number of photons that hit a given area in a given time when it is illuminated by beam PPP is (A) twice, (B) the same, or (C) one-half of the number that hit when the area is illuminated by beam QQQ ?

The work function WWW for copper is 4.65eV4.65 \mathrm{eV}4.65eV . Visible light will dislodge electrons from a copper surface.

If you want to design a phototube that is able to respond to all visible light wavelengths, what should its cathode's work function be?

If you want to design a phototube that ignores all visible light, what should its cathode's work function be?

Violet light with a wavelength of 430 nm430 \mathrm{~nm}430 nm falls on a sodium plate (W=2.75eV) (W=2.75 \mathrm{eV}) (W=2.75eV) and a potassium plate (W=(W=(W= 2.30eV) 2.30 \mathrm{eV}) 2.30eV) . Which of of the following statements is true?

A long-wavelength photon, because it is larger, carries more total energy than a short-wavelength photon.

A beam of light $P$ has twice the wavelength but the same intensity as beam $Q$ . The number of photons that hit a given area in a given time when it is illuminated by beam $P$ is (A) twice, (B) the same, or (C) one-half of the number that hit when the area is illuminated by beam $Q$ ?

The work function $W$ for copper is $4.65 \mathrm{eV}$ . Visible light will dislodge electrons from a copper surface.

Violet light with a wavelength of $430 \mathrm{~nm}$ falls on a sodium plate $(W=2.75 \mathrm{eV})$ and a potassium plate $(W=$ $2.30 \mathrm{eV})$ . Which of of the following statements is true?