Deck 30: Quantum Physics

Question 1

The Compton effect justifies that light acts as photons.

Answer 1

True

Question 2

In quantum tunneling, electrons and other quantum particles can tunnel through a region of space that would be forbidden to them if they were classical particles.

Answer 2

True

Question 3

A photon is a particle with positive charge.

Answer 3

False

Question 4

The minimum amount of energy necessary to eject an electron from a metal surface is referred as Planck's constant.

Question 5

An ideal blackbody absorbs all of the light that is incident on it.

Question 6

In the spectrum of white light which one of the following colors corresponds to the highest temperature?

A) Yellow
B) Violet
C) Green
D) Red
E) Orange

Question 7

The de Broglie wavelength is inversely proportional to the momentum of the particle.

Question 8

The momentum of a photon is inversely proportional to its total energy.

Question 9

Which one of the following is true for the surface temperature of a bluish-white star in a constellation as compared to the red star in the same constellation?

A) It is greater.
B) It is less.
C) It is the same.

Question 10

The distribution of energy in the blackbody radiation depends upon the material from which the blackbody is constructed.

Question 11

A blackbody is a perfect emitter of the radiation it generates.

Question 12

Unlike other particles, photons have a finite momentum even though they have no mass.

Question 13

The rest mass of a photon is zero kg.

Question 14

If a beam of X-rays is scattered from protons instead of electrons, the change in the wavelength of this X-ray beam for a given angle of scattering decreases.

Question 15

Electrons come in discrete units of well defined mass and charge, but they also have wave properties.

Question 16

Which one of the following is the correct expression for the energy of the photon?

A) E = h/f
B) E = hλ/c
C) E = hc/λ
D) E = λc/h
E) E = hλ

Question 17

The energy of an ultraviolet photon is more than the energy of an infrared photon.

Question 18

The wavelength of a photon decreases when it is scattered from an electron.

Question 19

In the scattering of a photon striking an electron at rest, the energy of the incident photon is equal to the energy of scattered photon minus the final kinetic energy of the electron.

Question 20

A zero value for the Planck's constant would mean that the laws of classical physics would apply to quantum physics.

Question 21

The frequency of a light beam is doubled. Which one of the following is correct for the momentum of the photons in that beam of light?

A) It stays the same.
B) It is halved.
C) It is doubled.
D) It is reduced by one-fourth
E) It is quadrupled.

Question 22

The wavelength of a light beam is doubled. Which one of the following is correct for the momentum of photons for that light beam?

A) It is halved.
B) It stays the same.
C) It is doubled.
D) It is reduced by one-fourth
E) It is quadrupled.

Question 23

What happens to the frequency of the scattered X-rays beam as the scattering angle in the Compton effect decreases?

A) It stays the same.
B) It decreases.
C) It increases.
D) Not enough information

Question 24

Light of a given wavelength is used to illuminate the surface of a metal, however, no photoelectrons are emitted. In order to cause electrons to be ejected from the surface of this metal you should

A) use light of a longer wavelength.
B) use light of a shorter wavelength.
C) use light of the same wavelength but increase its intensity.
D) use light of the same wavelength but decrease its intensity.

Question 25

When you decrease, by a factor of two, the wavelength of the light causing photoelectrons to be emitted from a metal surface, the kinetic energy of the photoelectrons will

A) decrease by a factor of 2.
B) double
C) more than double.
D) increase by a factor of .
E) decrease by a factor of .

Question 26

Which one of the following is the correct expression of the cutoff frequency of the metal in terms of its work function?

A) f_o = W_o/h
B) f_o = W_o/c
C) f_o = c/W_o
D) f_o = h/W_o
E) None of the other choices is correct.

Question 27

If the wavelength of a photon is doubled, what happens to its energy?

A) It is halved.
B) It stays the same.
C) It is doubled.
D) It is quadrupled.
E) It is reduced by one-fourth.

Question 28

You perform Compton scattering experiments with X-rays of a fixed wavelength. In one experiment you scatter the X-rays from free electrons. In the second experiment you scatter the X-rays from protons instead. For X-rays scattered under a given angle, the wavelength change

A) will be larger for scattering from protons.
B) will be the same for both cases.
C) will be larger for scattering from electrons.
D) depends on the actual wavelength of the X-rays.

Question 29

Protons are being accelerated in a particle accelerator. When the speed of the protons is doubled, their de Broglie wavelength will

A) increase by a factor of 4.
B) increase by a factor of 2.
C) decrease by a factor of 2.
D) increase by a factor of .
E) decrease by a factor of .

Question 30

Which one of the following equations is correct for the maximum kinetic energy of photoelectrons ejected from a metal?

A) K_max = hc - W_o
B) K_max = hλ - W_o
C) K_max = hf - W_o
D) K_max = hλ/c - W_o
E) None of the other choices is correct.

Question 31

Which one of the following is the correct expression for the Heisenberg uncertainty principle?

A) Δp_yΔy ≥ h/2π
B) Δp_yΔy ≤ h/2π
C) Δp_y/Δy ≤ h/2π
D) Δy/Δp_y ≥ h/2π
E) None of the other answers is correct.

Question 32

Protons are being accelerated in a particle accelerator. When the energy of the protons is doubled, their de Broglie wavelength will

A) increase by a factor of 4.
B) increase by a factor of 2.
C) decrease by a factor of 2.
D) increase by a factor of .
E) decrease by a factor of .

Question 33

Our bodies, at 37.°C, emit radiation which peaks at what wavelength?

Question 34

In the spectrum of white light which one of the following colors corresponds to the lowest temperature?

A) Yellow
B) Blue
C) Red
D) Green
E) Orange

Question 35

Which of the following is the correct equation for the momentum of a photon?

A) p = (hc)/λ
B) p = λ/c
C) p = (hc)/f
D) p = (hf)/c
E) p = (hλ)/c

Question 36

If the position of an electron is measured very precisely there is an uncertainty in measuring its

A) kinetic energy.
B) momentum.
C) potential energy.
D) thermal energy.
E) None of the other answers is correct.

Question 37

What scattering angle in the Compton effect produces the minimum change in frequency?

A) 45°
B) 90°
C) 0°
D) 180°
E) 270°

Question 38

A proton and an electron are both accelerated to the same final kinetic energy. If λ_p is the de Broglie wavelength of the proton and λ_e is the de Broglie wavelength of the electron, then

A) λ_p > λ_e.
B) λ_p = λ_e.
C) λ_p < λ_e.
D) Not enough data to answer this question.

Question 39

If the frequency of a photon is halved, what happens to its energy?

A) It is doubled.
B) It is halved.
C) It is tripled.
D) It is quadrupled.
E) It is reduced by one-fourth.

Question 40

A proton and an electron are both accelerated to the same final speed. If λ_p is the de Broglie wavelength of the proton and λ_e is the de Broglie wavelength of the electron, then

A) λ_p > λ_e.
B) λ_p = λ_e.
C) λ_p < λ_e.
D) Not enough data to answer this question.

Question 41

What is the energy, in eV, of a photon of wavelength 550. nm?

Question 42

X-rays with a wavelength of 0.00100 nm are scattered by free electrons at 130°. What is the kinetic energy of each recoil electron?

Question 43

If the threshold wavelength to dislodge electrons from a metal is 373. nm, what is the work function?

Question 44

What would be the deBroglie wavelength for 1 gram moving at "escape speed" 25,000. mph?

Question 45

A small gas laser of the type used in classrooms may radiate light at a power level of 2.0 mW. If the wavelength of the emitted light is 642. nm, how many photons are emitted per second?

Question 46

Atoms in crystals are typically separated by distances of 0.10 nm. What KE must an electron have, in eV, in order to have a wavelength of 0.10 nm?

Question 47

How "slow" must a 200. gram ball move to have a deBroglie wavelength of 1.0 mm?

Question 48

If in Compton scattering of X-rays from a metal, the wavelength increases by 5% at an angle of 60°, what was the original wavelength before scattering?

Question 49

The cosmic background radiation permeating the universe has the spectrum of a 2.7 K thermal radiator. What is the peak wavelength?

Question 50

At what rate are photons emitted by a 50. W sodium vapor lamp?
(Assume that the lamp's light is monochromatic and of wavelength 589. nm.)

Question 51

Mathilda collects photoelectric data in her physics laboratory. She measures a stopping potential of 5.82 volts for radiation of wavelength 100. nm, and 17.99 volts stops 50.0 nm.
(a) What is the work function for the material in eV?
(b) From her data one determines Planck's constant to be what?

Question 52

A metallic surface is illuminated with light of wavelength 400. nm. If the work function for this metal is 2.4 eV, calculate the kinetic energy of the ejected electrons, in electron-volts.

Question 53

Through what potential must an electron be accelerated to observe maximum diffraction at 70.0° to the surface of a crystal with 0.334 nm between surface planes?

Question 54

What primary wavelength and corresponding photon energy is emitted by a body at:
(a) 400.°C?
(b) 800.°C?
(c) 1200.°C?

Question 55

What is the wavelength of a photon of energy 2.00 eV?

Question 56

A metallic surface has a work function of 2.50 eV. What is the longest wavelength that will eject electrons from the surface of this metal?

Question 57

A 140. KeV photon strikes an electron and scatters through an angle of 120.°
(a) What is the wavelength of the photon before scattering?
(b) What is the photon wavelength after scattering?

Question 58

FIGURE 30-1
The graph shown in Figure 30-1 is a plot based on student data from their testing of a
photoelectric material.
(a) Determine the cutoff frequency.
(b) Determine the work function.

Question 59

The human eye can just detect green light of wavelength 500. nm, which arrives at the retina at the rate of 2 × W. How many photons arrive each second?

Question 60

What are the shortest wavelength X-rays produced by a 50,000-V X-ray tube?

Question 61

A proton, moving freely, has a wavelength of 0.600 pm.
(a) What is its momentum?
(b) What is its speed?
(c) Through what potential difference might it have been accelerated through, from rest, to reach this speed?

Question 62

What is the energy of a photon with a frequency of 6.60 × 10¹⁵ Hz?

A) 27.3 eV
B) 12.3 eV
C) 18.1 eV
D) 19.6 eV
E) 6.60 eV

Question 63

The surface temperature of the star is 6000 K. What is the wavelength associated with the light emitted by this star?

A) 850 nm
B) 907 nm
C) 311 nm
D) 492 nm
E) 502 nm

Question 64

A photon has energy of 4.20 eV. To what wavelength does this energy correspond?

A) 321 nm
B) 103 nm
C) 296 nm
D) 412 nm
E) 420 nm

Question 65

An electron determined to be at y = 2.000 ± 0.0010 cm has what minimum uncertainty in velocity?

Question 66

A photon has an energy of 6.60 eV. To what wavelength does this energy correspond?

A) 100 nm
B) 118 nm
C) 151 nm
D) 173 nm
E) 189 nm

Question 67

An electron is moving with speed 21. m/s.
(a) What is its deBroglie wavelength?
(b) What Diffraction Grating spacing between slits would give a 1st order maximum at 30.0°?

Question 68

What is the cutoff frequency for a metal surface that has a work function of 5.42 eV?

A) 1.31 × 10¹⁵ Hz
B) 2.01 × 10¹⁵ Hz
C) 3.01 × 10¹⁵ Hz
D) 5.02 × 10¹⁵ Hz
E) 6.04 × 10¹⁵ Hz

Question 69

Suppose that the speed of an electron traveling 1.0 km/s is known to an accuracy of 1 part in 10⁵ (i.e., within 0.01%). What is the greatest possible accuracy within which we can determine the position of this electron?

Question 70

A 2.00 kg mass is attached to a spring with a spring constant of 48.0 N/m. If the maximum speed of the mass in this system is 1.14 m/s, what is the energy of the quanta of energy in this system?

A) 2.23 × 10^-34 J
B) 6.63 J
C) 6.63 × 10^-34 J
D) 5.17 J
E) 5.17 × 10^-34 J

Question 71

What is the surface temperature of a star, given that its radiation peak occurs at a frequency of 1.06 × 10¹⁵ Hz?

A) 17,000 K
B) 14,500 K
C) 19,000 K
D) 20,400 K
E) 18,000 K

Question 72

An electron is trapped in a box of width 0.10 nm. What is the wavelength of the photon emitted when an electron makes a transition from the n = 3 to the n = 1 state?

Question 73

A 60-W bulb is operating at an efficiency of 6.20%. What is the number of photons per second given off by the bulb assuming the wavelength of light to be 580 nm?

A) 5.42 × 10¹⁸ photons/s
B) 10.8 × 10¹⁸ photons/s
C) 16.2 × 10¹⁸ photons/s
D) 21.7 × 10¹⁸ photons/s
E) 25.3 × 10¹⁸ photons/s

Question 74

An electron is known to be confined to a region of width 0.10 nm. What is an approximate expression for the least kinetic energy it could have, expressed in eV?

Question 75

The excited state of a certain atom is 3.2 eV ± 0.21 eV.
(a) What is the average lifetime of this state?
(b) If the excited energy doubled (6.4 eV ± 0.21 eV) how would the lifetime be affected?

Question 76

Which one of the following is correct for the energy of a 620 nm beam of light?

A) 1.60 × 10^-19 eV
B) 2.10 × 10^-19 J
C) 3.21 × 10^-19 J
D) 1.60 × 10^-18 eV
E) 3.21 × 10^-18 eV

Question 77

The work function of a certain metal is 1.90 eV. What is the longest wavelength of light that can cause photoelectron emission from this metal?

A) 231 nm
B) 14.0 nm
C) 62.4 nm
D) 344 nm
E) 653 nm

Question 78

The radius of a typical nucleus is about 5.0 × 10^-15 m. Assuming this to be the uncertainty in the position of a proton in the nucleus, estimate the uncertainty in the proton's energy (in eV).

Question 79

What is the number of photons per second given off by a light bulb with a power of 100 Watts operating at an efficiency of 4.80%? Assume the wavelength of light to be 600 nm.

A) 6.34 × 10¹⁸ photons/s
B) 5.42 × 10¹⁸ photons/s
C) 3.11 × 10¹⁸ photons/s
D) 25.3 × 10¹⁸ photons/s
E) 14.5 × 10¹⁸ photons/s

Question 80

A crystal diffracted a beam of electrons. The crystal spacing was 0.18 nm and the maximum scattering occurred at 80.° relative to the surface normal. The electrons were directed normally onto the crystal.
(a) What is the wavelength of the electrons?
(b) What potential difference accelerated the electrons?