Name
Class
Date
Assessment
Atomic Physics
Section Quiz: Quantization of Energy
Write the letter of the correct answer in the space provided.
______ 1. Which of the following phrases correctly describes a blackbody?
a. object from which neither light nor matter escapes
b. absorbs all radiation and emits no radiation
c. emits all radiation and absorbs no radiation
d. perfectly absorbs and emits all radiation
______ 2. Classical electromagnetic theory predicted that the energy radiated by
a blackbody would become infinite as the wavelength of the radiation
became shorter. What was the contradiction between observation and
this result called?
a. the Compton shift
b. the ultraviolet catastrophe
c. the photoelectric effect
d. the quantum theory
______ 3. Which of the following statements is true about the energy of a
quantum of radiation?
a. Energy increases with wavelength.
b. Energy increases with frequency.
c. Energy increases with intensity.
d. Energy increases with speed.
______ 4. What is the energy of a photon with a frequency of 5.45 1014 Hz?
(h 6.63 1034 J•s)
a. 3.61 1019 J
b. 3.61 1034 J
c. 3.65 1040 J
d. 1.22 1048 J
______ 5. What is the frequency of a photon with an energy of 1.3 1019 J?
(h = 6.63 1034 J•s)
a. 8.6 1020 Hz
b. 1.5 106 Hz
c. 2.0 1014 Hz
d. 1.2 1052 Hz
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Holt Physics
137
Quiz
Name
Class
Date
Atomic Physics continued
______ 6. For a photoelectron to be emitted by a metal that is exposed to photons, the energy of the photons must be greater than what property of
the metal?
a. its threshold frequency
b. its ionization energy
c. its electronegativity
d. its work function
______ 7. A metal with a work function of 3.5 eV is exposed to photons with an
energy of 3.7 eV. What is the maximum kinetic energy of the emitted
photoelectrons?
a. 7.2 eV
b. 3.7 eV
c. 3.5 eV
d. 0.2 eV
______ 8. Which of the following statements correctly describes the Compton
shift that occurs when photons scatter from electrons?
a. Electron momentum decreases as electrons scatter from photons.
b. Photon wavelengths shorten as they gain energy from electrons.
c. Photon wavelengths lengthen as they lose energy to electrons.
d. Scattered photons interfere with each other at different angles.
9. Explain why the concept of quanta was required to make theoretical predictions for blackbody radiation match the experimental observations.
10. Photons with a frequency of 6.6 1014 Hz shine on the surface of a metal
with a work function of 2.4 eV. What is the maximum kinetic energy of the
emitted photoelectrons? (h 6.63 1034 J•s; 1 eV 1.6 1019 J)
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Holt Physics
138
Quiz
TEACHER RESOURCE PAGE
10. Answers may vary. Sample answer:
10. 0.3 eV
Microwaves have long wavelengths,
low frequency, and relatively low
energy. Microwaves are used to cook
food, transmit telephone, computer
and satellite data, and radar.
Given
f 6.6 1014 Hz
hft 2.4 eV
h 6.63 1034 J•s
1 eV 1.6 1019 J
Solution
KEmax hf hft
KEmax (6.63 1034 J•s)(6.6 1014 Hz) 21 Atomic Physics
QUANTIZATION OF ENERGY
1.
2.
3.
4.
d
b
b
a
Given
f 5.45 1014 Hz
h 6.63 1034 J•s
Solution
E hf (6.63 1034 J•s)(5.45 1014 Hz)
3.61 1019 J
5. c
Given
E 1.3 1019 J
h 6.63 1034 J•s
Solution
E
1.3 1019 J
f h
6.63 1034 J•s
2.0 1014 Hz
6. d
7. d
Given
hf 3.7 eV
hft 3.5 eV
Solution
KEmax hf hft 3.7 eV 3.5 eV
0.2 eV
8. c
9. Classical electromagnetic theory predicted that, as the wavelength of light
approached zero, the amount of energy
emitted by a blackbody would become
infinite. By limiting the frequencies
that a blackbody could radiate to fixed
integral increments, Planck was able
to modify the classical theory so that
radiated energy reached a maximum
at a particular frequency and then
decreased toward zero, as was indicated by experimental results.
1eV
2.4 eV
1.60 1019 J
KEmax 2.7 eV 2.4 eV 0.3 eV
21 Atomic Physics
MODELS OF THE ATOM
1.
2.
3.
4.
9.
b
5. c
b
6. a
d
7. b
c
8. c
The Rutherford model of the atom had
a compact, massive nucleus that contained the positive charge of the atom.
The electrons orbited this nucleus in a
manner similar to planets orbiting the
sun. This model correctly accounted
for the nucleus, but according to classical electromagnetic theory, the orbiting electrons would radiate energy
continuously, and so could not maintain stable orbits. Also, Rutherford’s
model provided no explanation for
emission or absorption spectra.
10. In the Bohr model of the atom, electrons move in orbits around the
nucleus, much like planets orbit the
sun. However, only specific orbits are
stable and can thus be occupied by the
electrons. When electrons are in these
orbits, they do not emit radiation, as predicted by classical electromagnetic theory. Radiation is emitted when electrons
move from higher-energy levels to
lower-energy levels, which accounts for
the individual lines of emission spectra. However, Bohr’s model could not
explain why the stable orbits existed, or
why radiation was not emitted when the
electrons were in these orbits. The Bohr
model also did not predict the spectra
for atoms with more than one electron
in their outermost energy levels.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Holt Physics
172
Answer Key