Quantum Mechanics Section 1 Practice
Practice 1: Waves and Electron Volts
A light wave has a wavelength of 325 nm.
a. What is the speed of this wave?
b. What is the frequency of the wave?
2. A light wave has a frequency of 1.6 x 1015 Hz.
a. What is the speed of this wave?
b. What is the wavelength of this wave?
c. Compare this to a light wave with a frequency of 3 x 1015 Hz. Which wave has more enegy.
3. A particle has 4 eV of energy. State this energy in Joules.
4. A particle has 1.28 x 10-18 J of energy. State this energy in terms of eV.
1.
Practice 3: Intro to Photons
1.
A 50,000 W radio station transmits waves of wavelength 4 m. Which of the following is the best estimate of the
number of photons it emits per second?
(A) 108 (B) 1022 (C) 1030 (D) 1040 (E) 1056
2. What is the momentum of photons that have a wavelength of 620 nm?
3. What is the frequency of a photon that has the same momentum as an electron with speed 1200 m/s? The peak
wavelength for a 60 Watt incandescent light bulb is 555 nm.
a. What is the momentum of photons released by this bulb?
b. How many photons would be released by this light bulb in 3 seconds?
(Modified) AP Free Response
Practice 4: The Photoelectric Effect
1.
2. Light of a single frequency falls on a photoelectric material but no electrons are emitted. Electrons may be
emitted if the
A) frequency of light is decreased D) intensity of light is increased
B) frequency of light is increased E) velocity of light is increased
C) intensity of light is decreased
3. A student performs the photoelectric effect experiment and obtains the data depicted in the accompanying
graph of Ekm (max kinetic energy) of photoelectrons vs the frequency of the photons. What is the approximate
work function of this material?
A) 1.5 eV B) 2.0 eV C) 2.7 eV D) 4.0 eV E) 6.0 eV
4. Questions 4-5 relate to the photoelectric effect and the five graphs below
5.
Which graph best shows the maximum kinetic energy K of the photoelectrons as a function of the frequency of
incident light?
(A) A (B) B (C) C (D) D (E) E
6. Which graph best shows the maximum kinetic energy K of a photoelectron as a function of the intensity of
incident light?
(A) A (B) B (C) C (D) D (E) E
7. The work function for a metal is ϕ. What is the threshold frequency of incident light required for the emission of
photoelectrons from a cathode made of that metal?
A) ϕ / h B) h / ϕ C) ϕh D) ϕ / hc E) hc / ϕ
1980B3
1980B3. In a photoelectric experiment, radiation of several different frequencies was made to shine on a metal surface and the
maximum kinetic energy of the ejected electrons was measured at each frequency. Selected results of the experiment are presented in
the table:
a. On the axes below, plot the data from this photoelectric experiment.
b. Determine the threshold frequency of the metal surface.
c. Determine the work function of the metal surface.
d. When light of frequency 2.0 x 1015 hertz strikes the metal surface, electrons of assorted speeds are ejected from the surface. What
minimum retarding potential would be required to stop all of the electrons ejected from the surface by light of frequency 2.0 x 1015
hertz?
e. Investigation reveals that some electrons ejected from the metal surface move in circular paths. Suggest a reasonable explanation for
this electron behavior.