AP® Physics 2
Myers Park High School
Problem Set: Light and the Photoelectric Effect
Solve the following problems. Answers are at the end of the problem set.
1.
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) 3.11 × 1018 photons/s
C) 25.3 × 1018 photons/s
D) 14.5 × 1018 photons/s
2.
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
3.
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
4.
A photon has an energy of 7.80 eV. To what wavelength does this energy correspond?
A) 100 nm
B) 151 nm
C) 173 nm
D) 159 nm
5.
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) 344 nm
D) 653 nm
6.
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) 564 nm
D) 610 nm
7.
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.
8.
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.
1
AP® Physics 2
Myers Park High School
9.
Problem Set: Light and the Photoelectric Effect
What is the cutoff frequency for a metal surface that has a work function of 6.22 eV?
A) 1.50 × 1015 Hz
B) 2.01 × 1015 Hz
C) 3.01 × 1015 Hz
D) 5.02 × 1015 Hz
10. 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) 0.48 × 10-19 J
D) 0.33 × 10-19 J
11. Light with a frequency of 9.50 × 1014 Hz is incident on a metal that has a work function of 3.1 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) 1.33 × 10-19 J
D) 2.41 × 10-19 J
12. 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) 5.92 × 1014 Hz
Questions 13-14 relate to photoelectric effect and the five graphs below
13. Which graph best shows the maximum kinetic energy K of the electrons as a function of the
frequency of incident light?
(A) A (B) B (C) C (D) D (E) E
14. Which graph best shows the maximum kinetic energy K of the photoelectrons as a function of the
intensity of incident light?
(A) A (B) B (C) C (D) D (E) E
15. With regard to the photoelectric effect, which one of the following would lead to an increase in
the maximum kinetic energy of the ejected electrons?
(A) Increasing the number of photons per second striking the surface.
(B) Using photons whose frequency is less than Wo/h, where Wo is the work function of the metal
and h is Planck’s constant.
(C) Increasing the frequency of the incident light.
(D) Selecting a metal that has a greater work function.
(E) Selecting a metal that has a larger resistivity.
2
AP® Physics 2
Myers Park High School
Problem Set: Light and the Photoelectric Effect
16. Which of the following graphs best represents the de Broglie wavelength  of a particle as a
function of the linear momentum p of the particle?
17. Of the following phenomena, which provides the best evidence that particles can have wave
properties?
(A) The absorption of photons by electrons in an atom
(B) The alpha-decay of radioactive nuclei
(C) The interference pattern produced by neutrons incident on a crystal
(D) The production of x-rays by electrons striking a metal target
(E) The scattering of photons by electrons at rest
18. Which of the following phenomena is evidence for the photon model of light?
(A) blackbody radiation
(B) the Compton effect
(C) the photoelectric effect
(D) all of the above
(E) none of the above
19. In the photoelectric effect, the maximum speed of the electrons emitted by a metal surface when
it is illuminated by light depends on which of the following?
I. Intensity of the light
II. Frequency of the light
III. Nature of the photoelectric surface
(A) I only
(B) III only
(C) I and II only
(D) II and III only
(E) I, II, and III
20. The quantity  in the photoelectric equation is the _____.
(A) energy difference between the two lowest electron orbits in the atoms of the metal surface
(B) total light energy absorbed by the metal surface during the measurement
(C) minimum energy a photon must have in order to be absorbed by the metal surface
(D) minimum energy required to free an electron from its binding to the metal material
(E) average energy of all electrons in the metal surface
21. An electron and a proton have the same wavelength. Which one of the following statements is
correct about them?
(A) The momentum of the proton is less than that of the electron
(B) The momentum of the proton is greater than that of the electron
(C) They have the same speed
(D) The kinetic energy of the proton is greater than that of the electron
(E) The kinetic energy of the proton is less than that of the electron
3
AP® Physics 2
Myers Park High School
Problem Set: Light and the Photoelectric Effect
22. In an experiment on photoelectric effect, a photoelectric target is irradiated with laser beams of
various frequencies and in each case the stopping potential is measured. When a graph of
stopping potential vs. frequency is plotted, it is found to be a linear relationship. The slope of this
line is equal to
(A) h/e
(B) h
(C) 
(D)  / e
(E)  / h
23. A laser source gives light output of power P. If the wavelength of the laser is λ, the number of
photons emitted in a time t in terms of the given parameters and fundamental constants is
(A) Pλt/hc
(B) Phct/λ
(C) Pht/λc
(D) Pλ/h
(E) Pct/hλ
24. Determine the wavelength of the photon emitted when an electron falls from an excited state (n=2
and -3.4eV) to the ground state (n=1 and -13.6eV) in a hydrogen atom?
(A) 122 nm
(B) 188 nm
(C) 242 nm
(D) 310 nm
25. A Lithium atom with an atomic number of 3 is excited as electromagnetic radiation is incident
upon it.
a. Determine the ground state energy for a Lithium electron.
b. Determine the wavelength of light (radiation) that would cause an electron to jump from
the ground state to an excited state where n=2.
c. Determine the minimum wavelength of light that will ionize the Lithium atom?
26. How much energy is needed to ionize a hydrogen atom (atomic number 1) in the n=2 state?
27. What wavelength photon would be required to ionize a hydrogen atom at ground state and give the
ejected electron a kinetic energy of 10 eV?
1.
6.
11.
16.
21.
D
C
C
D
E
26. 3.4 eV
2.
7.
12.
17.
22.
B
B
D
C
A
27. 5.26 x 10-8m
3.
8.
13.
18.
23.
A
A
A
D
A
4.
9.
14.
19.
24.
28.
29.
4
D
A
E
D
A
5.
10.
15.
20.
25.
30.
D
D
C
D
a. -122.4 eV
b. 13.5 nm
c.10.1 nm