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Physics 30: Chapter 6 Exam – Particle Nature of Light
Name: _________________________ Date: _____________
Mark: ____/34
Numeric Response. Place your answers to the numeric response questions, with units, in the
blanks at the side of the page. (1 mark each)
1.
Determine the frequency of a photon that has an energy of
1.25 x 10-18 J.
2.
Calculate the wavelength a photon having an energy of 3.80 eV.
3.
Determine the threshold frequency of light shining on a metal that has
a work function of 2.32 eV.
4.
X-rays having an energy of 17.0 keV strike a metal plate causing
electrons to be ejected along with X-rays that have an energy of
15.0 keV. Calculate the kinetic energy of the ejected electrons.
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Written Response. Show all your work. Clearly identify your final answer(s) rounded off to the
proper number of significant digits.
1.
Scattered X-rays
X-rays strike a metal plate causing
electrons to be ejected along with
scattered X-rays as shown in the diagram.
Momentum must be conserved.
metal
foil
Incident X-rays
45.0°

e-
a. Complete the chart. (1 mark each)
Momentum
x-component
(x 10-23 kg•m/s)
y-component
(x 10-23 kg•m/s)
Incident
X-ray
Scattered
X-ray
Target
Electron
5.50
0
0
2.50
0
b. Determine the velocity of the ejected electron. (3 marks)
c. Determine the wavelength of the scattered X-ray. (3 marks)
2
Scattered
Electron
Multiple Choice: Select the best answer. Mark it clearly on your Scantron. (1 mark each)
1.
Determine the amount of quantized energy for a photon having a frequency of 3.85 x 1014 Hz.
a.
1.28 x 106 J
b.
1.28 x 10-19 J
c.
2.55 x 106 J
d.
2.55 x 10-19 J
2.
The energy of a photon of light with a wavelength of 5.0 x 10-7 m is
a.
2.5 eV
b.
4.0 x 10-16 J
c.
8.0 x 10-26 J
d.
3.4 eV
3.
A beam of monochromatic light having a wavelength of 580 nm is incident on a detector. The
beam delivers 2.88 x 10-16 J of energy to the detector each second. Determine the number of
photons incident on the detector each second.
a.
8.11 x 1011
b.
840
c.
119
d.
1.19 x 109
4.
A quantum of EMR is called a(n)
a.
gluon
b.
electron
c.
photon
d.
compression wave
5.
Identify the phenomena that suggest EMR must be treated as a particle.
a.
photoelectric effect, Compton Effect, diffraction
b.
interference, photoelectric effect, diffraction
c.
photoelectric effect, Compton Effect
d.
diffraction, interference, refraction
6.
Zinc has a work function of 4.0 eV and is used in a photoelectric cell with light of an energy of
19 eV per photon. Determine the maximum kinetic energy of photoelectrons leaving the cell
a.
11 eV
b.
15 eV
c.
19 eV
d.
23 eV
7.
The intensity of light is manipulated in a photoelectric experiment. When its frequency is
above the threshold frequency, the
a.
energy of each photoelectron will change
b.
maximum kinetic energy of the electrons will change
c.
number of photoelectrons will change
d.
frequency of the incident photons will change
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8.
Radiation with a frequency of 7.52 x 1014 Hz is incident on a photoelectric surface. A stopping
voltage of 0.916 V is required to reduce the current through the cell to zero. The work
function of the photoelectric surface is
a.
1.10 eV
b.
4.80 x 10-19 J
c.
1.47 x 10-19 J
d.
2.20 eV
Use the information below to answer question 9.
The stopping voltage of electrons released
through a photoelectric process may be
determined using the following apparatus.
Y
X
9.
The identity of the two meters, X and Y are
X
Y
a.
ammeter
voltmeter
b.
parking meter
ammeter
c.
voltmeter
ammeter
d.
ohmmeter
voltmeter
Use the information below to answer question 10.
A graph of stopping voltage as a function of frequency
for a photoelectric experiment is shown to the right.
Stopping voltage
Stopping voltage as a
function of Frequency
III
Frequency
II
I
10.
Identify the meaning of the three sections of the graph.
a.
b.
c.
d.
I
threshold frequency
work function
Planck’s constant
work function
II
work function
Planck’s constant
work function
threshold frequency
4
III
Planck’s constant
threshold frequency
threshold frequency
Planck’s constant
Use the information below to answer question 11.
A student is making an analogy for light as a photon (quantized) and light as a wave (continuous).
The analogy she uses involves walking to a height using a ramp or stairs.
i.
ii.
wave
ramp
iii.
iv.
Particle (photon)
stairs
11.
Match the items that best represent an analogue (i.e., continuous) system and the items that
best represent a quantized system.
analogue
Ramp and wave
Ramp and particle
Ramp and stairs
Wave and particle
a.
b.
c.
d.
quantized
Stairs and particle
Stairs and waves
Wave and particle
Ramp and stairs
Use the following four graphs to answer question 12.
12.
photocurrent
D
photocurrent
C
photocurrent
B
photocurrent
A
The graph that best represents a plot of photocurrent as a function of intensity of incident
light for the photoelectric effect is
a.
A
b.
B
c.
C
d.
D
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Use the information below to answer question 13.
An X-ray photon collides with an electron to produce a scattered photon as shown below.
Scattered X-ray photon
Incident X-ray photon
13.
Identify the momentum vector below that best describes the path of the electron after the
collision.
a.
b.
c.
d.
14.
A photon having an energy of 4.0 eV strikes an electron in an atom on the surface of a metal
plate. The effect that is most likely to occur is
a.
Compton scattering
b.
the Photoelectric effect
c.
Rutherford scattering
d.
polarization
15.
Determine the momentum of a photon of light having an energy of 7.87 x 10-16 J.
a.
3.81 x 10-23 kg•m/s
b.
2.36 x 10-7 kg•m/s
c.
2.62 x 10-24 kg•m/s
d.
7.17 x 10-46 kg•m/s
16.
Determine the momentum of a photon having a wavelength of 3.00 x 10-8 m.
a.
2.21 x 1026 kg•m/s
b.
1.99 x 10-41 kg•m/s
c.
4.52 x 1025 kg•m/s
d.
2.21 x 10-26 kg•m/s
17.
A photon whose frequency is 2.0 x 1015 Hz has a momentum of
a.
1.3 x 10-18 kg•m/s
b.
4.4 x 10-27 kg•m/s
c.
3.3 x 10-48 kg•m/s
d.
1.1 x 10-57 kg•m/s
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18.
The wavelength of the scattered X-ray will be
a.
greater than the wavelength of the incident X-ray
b.
less than the wavelength of the incident X-ray
c.
equal to the wavelength of the incident X-ray
d.
greater or less depending on the frequency of the X-ray.
19.
A Crookes tube is used with a potential difference of 70.0 kV between the cathode and anode.
Determine the maximum possible momentum of each X-ray photon produced.
a.
3.73 x 10-23 kg•m/s
b.
1.69 x 10-23 kg•m/s
c.
1.69 x 1019 kg•m/s
d.
3.73 x 1019 kg•m/s
20.
X-rays having a wavelength of 5.00 x 10-11 m strike a metal plate and eject electrons along with
scattered X-rays having a wavelength of 8.00 x 10-11 m. Determine the speed of the ejected
electrons.
a.
3.27 x 1015 m/s
b.
1.19 x 108 m/s
c.
1.42 x 1016 m/s
d.
5.72 x 107 m/s
21.
X-rays strike a metal plate causing the
ejection of electrons as shown in the
diagram. Determine the wavelength of
the scattered X-rays.
Scattered X-rays
metal
4.42 x 10
-11
m X-rays
foil
24.1°
e-
a.
b.
c.
d.
2.11 x 10-13 m
4.44 x 10-11 m
4.40 x 10-11 m
4.54 x 10-11 m
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