The Atom
Practice Test
1.
According to Figure 27-6, what is the approximate frequency needed to eject an electron with a minimum kinetic energy of 2 eV?
a.
10×10
14
Hz
b.
8.1×10
14
Hz
c.
4.5×10
14
Hz
d.
9.2×10
14
Hz
Hint
2.
A mass spectrometer analyzes and gives data for a beam of doubly ionized atoms. The values are
q
= 3.20×10
-19
C,
B
= 4.0×10
-2
T,
r
= 0.220 m, and
V
= 45 V. Find the mass of one of these atoms.
a.
8.7×10
-21
kg
b.
2.8×10
-25
kg
c.
2.4×10
-16
kg
d.
4.3×10
-26
kg
Hint
3.
An alternating current source produces changing currents in a wire connected to it. This wire generates electromagnetic fields. What is this wire called?
a.
an antenna
b.
a polarizer
c.
a capacitor
d.
an oscillator
Hint
4.
If the charge of an atom's nucleus is +2 and the charge of the surrounding electrons is -2, the atom is __________.
a.
electrically neutral
b.
negatively-charged
c.
positively-charged
d.
unstable
Hint
5.
The __________ is the minimum frequency of radiation required in order to eject electrons from a metal.
a.
photon momentum
b.
de Broglie wavelength
c.
kinetic frequency
d.
threshold frequency
Hint
6.
In Figure 20-8, if the charge on the rod were decreased, what effect, if any, would this have on the final result?
a.
The left sphere would be negatively charged and the right sphere would be positively charged, with the same amount of charge as in the original picture c.
b.
It would have no effect.
c.
The left sphere would still be positive and the right sphere would still be negative, but there would be more total charge on each.
d.
The left sphere would still be positive and the right sphere would still be negative, but there would be less total charge on each.
Hint
7.
When an electron drops from
E
4
to
E
3
in an excited hydrogen atom, the frequency of the emitted photon is 1.60×10
14
Hz. What is its wavelength?
a.
188 nm
b.
941 nm
c.
632 nm
d.
1880 nm
Hint
8.
In Figure 20-11a, if
q
1
is 2.0 mC,
q
2
is 3.0 mC, and the separation between them is 2.5 m, what is the magnitude of the force between them?
a.
8600 N
b.
220,000 N
c.
5400 N
d.
2.4 N
Hint
9.
An electric field is to be measured using a positive test charge of 3.0×10
-5
C. This test charge experiences a force of 0.50 N acting at an angle of 15°. What is the magnitude of the electric field at the location of the test charge?
a.
1.7×10
3
N/C
b.
0.49 N/C
c.
6.0×10
-5
N/C
d.
1.7×10
4
N/C
Hint
10.
Materials through which electrical charges will not move easily are called __________.
a.
insulators
b.
grounders
c.
conductors
d.
ions
Hint
11.
The ratio of charge stored to electric potential difference is called the __________.
a.
resistance
b.
current
c.
capacitance
d.
capacitor
Hint
12.
Protons passing perpendicular to and without deflection through a uniform magnetic field of 0.54 T are balanced by a 5.4×10
3
-N/C electric field. What is the speed of the moving protons?
a.
1.0×10
-4
m/s
b.
9.0×10
- 3
m/s
c.
1.0×10
4
m/s
d.
9.0×10
3
m/s
Hint
13.
Which of the following represents the Bohr quantization condition?
a.
2
πrh
=
nλ
b.
2
n
=
λπr
c.
nλ
= 2
πr
d.
r
/
λ
=
h
/2
π
Hint
14.
Determine the frequency of the photon emitted when an electron drops from
E
5
to
E
4
in an excited hydrogen atom.
a.
7.39×10
13
Hz
b.
4.89×10
13
Hz
c.
5.86×10
14
Hz
d.
3.55×10
14
Hz
Hint
15.
What device uses stimulated emission to produce an avalanche of photons, having the same wavelength and their minima and maxima at the same times?
a.
spectroscope
b.
semiconductor
c.
diffraction grating
d.
laser
Hint
16.
Energy carried in the form of electromagnetic waves is frequently called __________.
a.
terminal energy
b.
electromotive force
c.
electromagnetic radiation
d.
oscillating rays
Hint
17.
In the set-up of Figure 21-9, if the electric force up on a drop equals the gravitational force down on the drop, the drop ___.
a.
must be stationary
b.
will accelerate up
c.
will accelerate down
d.
could move upward at constant speed
Hint
18.
The __________ is a vector quantity that relates the force on a test charge to the size of the charge.
a.
equipotential
b.
potential
c.
capacitor
d.
electric field
Hint
19.
The work function for a certain element is 2.87 eV. What is its threshold wavelength?
hc
= 1240 eV·nm
a.
432 nm
b.
446 m
c.
356 nm
d.
495 nm
Hint
20.
According to Figure 27-6, what is the approximate frequency needed to eject an electron with a minimum kinetic energy of 5 eV?
a.
16×10
14
Hz
b.
12×10
14
Hz
c.
20×10
14
Hz
d.
It cannot be determined from the graph.
Hint
