Quiz 30: Quantum Physics

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

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

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

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

A photon is a particle with positive charge.

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

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

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

The rest mass of a photon is zero kg.

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

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.

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.

The Compton effect justifies that light acts as photons.

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

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

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

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.

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

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.

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

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

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.

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.

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.

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 .

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.

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.

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

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.

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.

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.

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

What scattering angle in the Compton effect produces the minimum change in frequency? A) 45° B) 90° C) 0° D) 180° E) 270°

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 .

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 .

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.

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.

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.

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.

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

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

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

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.)

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.

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?

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

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?

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

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?

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

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?

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.

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?

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

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?

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?

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

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

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?

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?

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°?

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?

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?

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

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).

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?

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?

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?

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?

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

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

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

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

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

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

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

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

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

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

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

What is the longest wavelength of light that can cause photoelectron emission from a metal that has a work function of 2.20 eV? A) 417 nm B) 257 nm C) 344 nm D) 564 nm E) 610 nm

Light with a wavelength of 310 nm is incident on a metal that has a work function of 3.8 eV. What is the maximum kinetic energy that a photoelectron ejected in this process can have? A) 0.62 × 10^-19 J B) 0.21 × 10^-19 J C) 0.36 × 10^-19 J D) 0.48 × 10^-19 J E) 0.33 × 10^-19 J

Light with a frequency of 8.70 × 10¹⁴ Hz is incident on a metal that has a work function of 2.8 eV. What is the maximum kinetic energy that a photoelectron ejected in this process can have? A) 8.71 × 10^-19 J B) 3.11 × 10^-19 J C) 1.28 × 10^-19 J D) 2.41 × 10^-19 J E) 4.52 × 10^-19 J

A beam of light with a frequency range of 3.01 × 10¹⁴ Hz - 6.10 × 10¹⁴ Hz is incident on a metal surface. If the work function of the metal surface is 2.20 eV, what is the range of frequencies in this beam of light that will be responsible for ejecting electrons from this metal surface? A) 1.12 × 10¹⁴ Hz - 5.31 × 10¹⁴ Hz B) 1.12 × 10¹⁴ Hz - 3.10 × 10¹⁴ Hz C) 3.01 × 10¹⁴ Hz - 6.10 × 10¹⁴ Hz D) 5.31 × 10¹⁴ Hz - 6.10 × 10¹⁴ Hz E) None

A beam of light with a frequency range of 3.01 × 10¹⁴ Hz - 6.10 × 10¹⁴ Hz is incident on a metal surface. If the work function of the metal surface is 2.20 eV, what is the maximum kinetic energy of photoelectrons ejected from this surface? A) 0.32 eV B) 0.21 eV C) 0.42 eV D) 0.16 eV E) 0.48 eV

A beam of white light of a certain frequency is incident on a metal surface. If the work function of this surface is 2.20 eV, what frequency of light would give a maximum kinetic energy of 0.25 eV to the photoelectrons ejected from this surface? A) 2.05 × 10¹⁴ Hz B) 1.02 × 10¹⁴ Hz C) 2.50 × 10¹⁴ Hz D) 3.53 × 10¹⁴ Hz E) 5.92 × 10¹⁴ Hz

What is the momentum of a photon of light that has a frequency of 2.8 × 10¹⁴ Hz? A) 1.5 × 10^-28 kg∙m/s B) 2.1 × 10^-28 kg∙m/s C) 4.4 × 10^-28 kg∙m/s D) 6.3 × 10^-28 kg∙m/s E) 6.2 × 10^-28 kg∙m/s

What is the momentum of a photon of light that has a wavelength of 480 nm? A) 1.1 × 10^-27 kg∙m/s B) 2.2 × 10^-27 kg∙m/s C) 1.8 × 10^-27 kg∙m/s D) 1.4 × 10^-27 kg∙m/s E) 2.0 × 10^-27 kg∙m/s

A certain photon after being scattered from a free electron at rest moves at an angle of 120° with respect to the incident direction. If the wavelength of the incident photon is 0.611 nm, what is the kinetic energy of the recoiling electron? A) 1.5 × 10^-18 J B) 2.1 × 10^-18 J C) 3.1 × 10^-18 J D) 4.3 × 10^-18 J E) 5.2 × 10^-18 J

A certain photon after being scattered from a free electron at rest moves at an angle of 120° with respect to the incident direction. If the wavelength of the incident photon is 0.591 nm, what is the wavelength of the scattered photon? A) 0.380 nm B) 0 nm C) 0.550 nm D) 0.591 nm E) 0.595 nm

A certain photon after being scattered from a free electron at rest moves at an angle of 120° with respect to the incident direction. If the wavelength of the incident photon is 0.591 nm, what is the energy of the scattered photon? A) 1.05 × 10^-16 J B) 2.10 × 10^-16 J C) 5.71 × 10^-16 J D) 3.34 × 10^-16 J E) 4.21 × 10^-16 J

A beam of X-rays at a certain wavelength are scattered from a free electron at rest and the scattered beam is observed at 45.0° to the incident beam. What is the Compton shift? A) 1.75 × 10^-13 m B) 2.76 × 10^-13 m C) 0 m D) 3.56 × 10^-13 m E) 7.11 × 10^-13 m

If the momentum of an electron is 1.95 × 10^-27 kg∙m/s, what is its de Broglie wavelength? A) 340 nm B) 210 nm C) 170 nm D) 420 nm E) 520 nm

The de Broglie wavelength of an electron is 380 nm. What is the speed of this electron? A) 2.04 × 10³ m/s B) 3.83 × 10³ m/s C) 1.92 × 10³ m/s D) 4.12 × 10³ m/s E) 5.22 × 10³ m/s

An electron is moving with the speed of 1780 m/s. What is its de Broglie wavelength? A) 409 nm B) 302 nm C) 205 nm D) 420 nm E) 502 nm

A certain crystal has an interatomic spacing of 0.142 nm. If a beam of electrons moving with a speed of 1400 m/s is diffracted from this crystal, what is the de Broglie wavelength of the electron? A) 420 nm B) 130 nm C) 260 nm D) 502 nm E) 520 nm

A certain crystal has an interatomic spacing of 0.442 nm. A beam of neutrons moving with a speed of 1640 m/s is diffracted from the crystal. What is the de Broglie wavelength of the neutron? A) 0.121 nm B) 0 nm C) 0.241 nm D) 0.484 nm E) 0.682 nm

A certain crystal has an interatomic spacing of 0.442 nm. A beam of neutrons moving with a speed of 1640 m/s is diffracted from the crystal. What is the angle of the second interference maximum? A) 17.0° B) 21.0° C) 33.0° D) 60.0° E) 90.0°

What is the minimum uncertainty in determining the position of an electron if the speed of the electron is 6000 m/s within an accuracy of 0.004%? A) 0.105 mm B) 0.153 mm C) 0.241 mm D) 0.335 mm E) 0.483 mm

What is the uncertainty in determining the momentum of an electron if the speed of the electron is 6000 m/s within an accuracy of 0.004%? A) 1.09 × 10^-31 kg∙m/s B) 1.31 × 10^-31 kg∙m/s C) 2.19 × 10^-31 kg∙m/s D) 3.21 × 10^-31 kg∙m/s E) 4.38 × 10^-31 kg∙m/s