Physics

### 21.1Planck and Quantum Nature of Light

46.
Scientists once assumed that all frequencies of light were emitted with equal probability. Explain what the blackbody radiation curve would look like if this were the case.
1. The blackbody radiation curve would look like a circular path.
2. The blackbody radiation curve would look like an elliptical path.
3. The blackbody radiation curve would look like a vertical line.
4. The blackbody radiation curve would look like a horizontal line.
47.

Because there are more gradations to high frequency radiation than low frequency radiation, scientists also thought it possible that a curve titled the ultraviolet catastrophe would occur. Explain what the blackbody radiation curve would look like if this were the case.

1. The curve would steadily increase in intensity with increasing frequency.
2. The curve would steadily decrease in intensity with increasing frequency.
3. The curve would be much steeper than in the blackbody radiation graph.
4. The curve would be much flatter than in the blackbody radiation graph.
48.

Energy provided by a light exists in the following quantities: 150 J, 225 J, 300 J. Define one possible quantum of energy and provide an energy state that cannot exist with this quantum.

1. 65 J; 450 J cannot exist
2. 70 J; 450 J cannot exist
3. 75 J; 375 J cannot exist
4. 75 J; 100 J cannot exist
49.
Why is Planck’s recognition of quantum particles considered the dividing line between classical and modern physics?
1. Planck recognized that energy is quantized, which was in sync with the classical physics concepts but not in agreement with modern physics concepts.
2. Planck recognized that energy is quantized, which was in sync with modern physics concepts but not in agreement with classical physics concepts.
3. Prior to Planck’s hypothesis, all the classical physics calculations were valid for subatomic particles, but quantum physics calculations were not valid.
4. Prior to Planck’s hypothesis, all the classical physics calculations were not valid for macroscopic particles, but quantum physics calculations were valid.
50.

How many 500-mm microwave photons are needed to supply the 8 kJ of energy necessary to heat a cup of water by 10 degrees Celsius?

1. 8.05 × 1028 photons
2. 8.05 × 1026 photons
3. 2.01 × 1026 photons
4. 2.01 × 1028 photons
51.

What is the efficiency of a 100-W, 550-nm lightbulb if a photometer finds that 1 × 1020 photons are emitted each second?

1. 101 percent
2. 72 percent
3. 18 percent
4. 36 percent
52.
Rank the following regions of the electromagnetic spectrum by the amount of energy provided per photon: gamma, infrared, microwave, ultraviolet, radio, visible, X-ray.
1. radio, microwave, infrared, visible, ultraviolet, X-ray, gamma
2. radio, infrared, microwave, ultraviolet, visible, X-ray, gamma
3. radio, visible, microwave, infrared, ultraviolet, X-ray, gamma
4. radio, microwave, infrared, visible, ultraviolet, gamma, X-ray
53.
Why are photons of gamma rays and X-rays able to penetrate objects more successfully than ultraviolet radiation?
1. Photons of gamma rays and X-rays carry with them less energy.
2. Photons of gamma rays and X-rays have longer wavelengths.
3. Photons of gamma rays and X-rays have lower frequencies.
4. Photons of gamma rays and X-rays carry with them more energy.

### 21.2Einstein and the Photoelectric Effect

54.

According to wave theory, what is necessary to eject electrons from a surface?

1. Enough energy to overcome the binding energy of the electrons at the surface
2. A frequency that is higher than that of the electrons at the surface
3. Energy that is lower than the binding energy of the electrons at the surface
4. A very small number of photons
55.

What is the wavelength of EM radiation that ejects 2.00-eV electrons from calcium metal, given that the binding energy is 2.71 eV?

1. 16.1 × 105 m
2. 6.21 × 10−5 m
3. 9.94 × 10−26 m
4. 2.63 × 10-7 m
56.
Find the wavelength of photons that eject $0.100 hyphen eV$ electrons from potassium, given that the binding energy is $2.24 eV$.
1. $6.22 times 10 Superscript negative 7 Baseline m$
2. $5.92 times 10 Superscript negative 5 Baseline m$
3. $1.24 times 10 Superscript negative 5 Baseline m$
4. $5.31 times 10 Superscript negative 7 Baseline m$
57.
How do solar cells utilize the photoelectric effect?
1. A solar cell converts all photons that it absorbs to electrical energy using the photoelectric effect.
2. A solar cell converts all electrons that it absorbs to electrical energy using the photoelectric effect.
3. A solar cell absorbs the photons with energy less than the energy gap of the material of the solar cell and converts it to electrical energy using the photoelectric effect.
4. A solar cell absorbs the photons with energy greater than the energy gap of the material of the solar cell and converts it to electrical energy using the photoelectric effect.
58.
Explain the advantages of the photoelectric effect to other forms of energy transformation.
1. The photoelectric effect is able to work on the Sun’s natural energy.
2. The photoelectric effect is able to work on energy generated by burning fossil fuels.
3. The photoelectric effect can convert heat energy into electrical energy.
4. The photoelectric effect can convert electrical energy into light energy.

### 21.3The Dual Nature of Light

59.
Upon collision, what happens to the frequency of a photon?
1. The frequency of the photon will drop to zero.
2. The frequency of the photon will remain the same.
3. The frequency of the photon will increase.
4. The frequency of the photon will decrease.
60.
How does the momentum of a photon compare to the momentum of an electron of identical energy?
1. Momentum of the photon is greater than the momentum of an electron.
2. Momentum of the photon is less than the momentum of an electron.
3. Momentum of the photon is equal to the momentum of an electron.
4. Momentum of the photon is zero due to zero rest mass but the momentum of an electron is finite.
61.

A 500-nm photon strikes an electron and loses 20 percent of its energy. What is the new momentum of the photon?

1. 4.24 × 10−27 kg ⋅ m/s
2. 3.18 × 10−27 kg ⋅ m/s
3. 2.12 × 10−27 kg ⋅ m/s
4. 1.06 × 10−27 kg ⋅ m/s
62.

A 500-nm photon strikes an electron and loses 20 percent of its energy. What is the speed of the recoiling electron?

1. 7.18 × 105 m/s
2. 6.18 × 105 m/s
3. 5.18 × 105 m/s
4. 4.18 × 105 m/s
63.

When a photon strikes a solar sail, what is the direction of impulse on the photon?

1. parallel to the sail
2. perpendicular to the sail
3. tangential to the sail
4. opposite to the sail
64.
What is a fundamental difference between solar sails and sails that are used on sailboats?
1. Solar sails rely on disorganized strikes from light particles, while sailboats rely on disorganized strikes from air particles.
2. Solar sails rely on disorganized strikes from air particles, while sailboats rely on disorganized strikes from light particles.
3. Solar sails rely on organized strikes from air particles, while sailboats rely on organized strikes from light particles.
4. Solar sails rely on organized strikes from light particles, while sailboats rely on organized strikes from air particles.
65.

The wavelength of a particle is called the de Broglie wavelength, and it can be found with the equation $p=hλp=hλ$ .
Yes or no—Can the wavelength of an electron match that of a proton?

1. Yes, a slow-moving electron can achieve the same momentum as a slow-moving proton.
2. No, a fast-moving electron cannot achieve the same momentum, and hence the same wavelength, as a proton.
3. No, an electron can achieve the same momentum, and hence not the same wavelength, as a proton.
4. Yes, a fast-moving electron can achieve the same momentum, and hence have the same wavelength, as a slow-moving proton.
66.
Large objects can move with great momentum. Why then is it difficult to see their wave-like nature?
1. Their wavelength is equal to the object’s size.
2. Their wavelength is very small compared to the object’s size.
3. Their wavelength is very large compared to the object’s size.
4. Their frequency is very small compared to the object’s size.