Physics 43 Final Exam Practice Spring 2017
Print Name:___________________________________
1. Molly flies her rocket past Nick at constant velocity v. Molly and Nick both measure the time it takes the rocket,
from nose to tail, to pass Nick. Which of the following is true?
A. Nick measures a shorter time interval than Molly.
B. Molly measures a shorter time interval than Nick.
C. Both Molly and Nick measure the same amount of time.
2
Beth and Charles are at rest relative to each other. Anjay runs past at velocity v while holding a long pole
parallel to his motion. Anjay, Beth, and Charles each measure the length of the pole at the instant Anjay
passes Beth. Rank in order, from largest to smallest, the three lengths LA, LB, and LC.
A . LA = LB = LC
B. LB = LC > LA
C. LA > LB = LC
D. LA > LB > LC
E. LB > LC > LA
3. Monochromatic light strikes a metal surface and electrons are ejected from the metal. If the intensity of the light is
increased, what will happen to the ejection rate and maximum energy of the electrons?
A) greater ejection rate; same maximum energy
B) same ejection rate; greater maximum energy
C) greater ejection rate; greater maximum energy
D) same ejection rate; same maximum energy
4. A beam of red light and a beam of violet light each deliver the same power on a surface. For which beam is the
number of photons hitting the surface per second the greatest?
A) the red beam
B) the violet beam
C) It is the same for both beams
5. An atom has the energy levels shown. A photon with a wavelength of
620 nm has an energy of 2.0 eV. Do you expect to see a spectral line with
wavelength of 620 nm in this atom’s emission spectrum?
A. Yes.
B. No.
6. An atom has the energy levels shown. A photon with a wavelength of
620 nm has an energy of 2.0 eV. Do you expect to see a spectral line with
wavelength of 620 nm in this atom’s absorption spectrum?
A. Yes.
B. No.
7 .Consider the wave function for the free particle, ψ = Ae–ikx. At what
value of x is the particle most likely to be found at a given time?
a) at x = 0
b) at small nonzero values of x c) at large values of x
d) anywhere along the x axis
8. Consider an electron, a proton, and an alpha particle (a helium nucleus), each trapped separately in identical infinite
square wells. Which particle has the longest wavelength when the system is in the ground state?
a) the electron
b) the proton
c) the alpha particle
d) All three have the same wavelength.
9. If P(r) is the radial probability density function for an electron in the ground state of a hydrogen atom, the most
probable value for r can be found from
a. dP/dt
b. dP/dr
c.
 rP(r)4r dr
2
 rP(r)dr
d.
e. d2P/dr2
10. The half-life of cobalt-60 is 5.3 years, w hile that of strontium-90 is 28 years. Suppose you have a sample
of each, such that they initially contain equal numbers of atoms of these nuclides. H ow w ill the activities of
the samples compare?
A ) The activity of the cobalt-60 sample w ill be greater.
B) The activities cannot be compared w ithout more information.
C) The activities w ill be equal.
D) The activity of the strontium-90 sample w ill be greater.
11. If an element emits one alpha particle, its atomic number decreases by
A) two.
B) one.
C) four.
D) zero.
12. The s, p, d, f, symbols represent values of the quantum number
a. ms
b. n
c. m
d. 
e. mj
13. A proton and an antiproton each w ith total energy of 400 GeV collide head-on. What is the total energy
(particles + energy) released?
a.
zero
b.
400 Gev
c. 800 GeV
d. 1600 GeV
e.
2400 GeV
14. H omer says that w e can safely use nuclear pow er because all radioactive nuclei are gone after tw o half lives. M arge says that only the decay rate is zero after tw o half-lives. Which one, if either, is correct,
and w hy?
a.
b.
c.
d.
e.
H omer, because half of the nuclei disintegrate in each half-life.
M arge, because the number of decays per unit time is halved in each half-life.
H omer, because it’s safe to handle radioactive substances after tw o half-lives.
Both, because w hen all nuclei disintegrate the decay rate is also zero.
N either, because one quarter of the nuclei are left after tw o half-lives.
Problems. You must show work for ANY credit. Box Answers. Circle
1. A meter stick moves in the direction of its length through a laboratory. According to measurements taken in the laboratory, its
length is 0.31 m. The speed of the meter stick relative to the laboratory is:
A) 0.096c
B) 0.31c
C) 0.69c
D) 0.83c
E) 0.95c
2. Two events occur 100 m apart with an intervening time interval of 0.60 s. The speed of a reference frame in which they occur
at the same coordinate is:
A) 0 c
B) 0.25c
C) 0.56c
D) 1.1c
E) 1.8c
3. What is the temperature of a burner on an electric stove when its glow is barely visible, at a wavelength of 700 nm? Assume the
burner radiates as an ideal blackbody and that 700 nm represents the peak of its emission spectrum.
A) 41 K
B) 240 K
C) 410 K
D) 2400 K
E) 4100 K
4. The work function for a certain sample is 2.3 eV. The stopping potential for electrons ejected from the sample by 7.0  1014-Hz
electromagnetic radiation is:
A) 0 V
B) 0.60 V
C) 2.3 V
D) 2.9 V
E) 5.2 V
0
0
5. The rest-energy of the Z boson is 96 GeV. Using this information, find the maximum length of time a virtual Z
–19
can exist, in accordance w ith the uncertainty principle Et = . (1 eV = 1.6  10
J.)
a.
b.
c.
d.
e.
–27
6.9  10
s
–30
7.5  10
s
–24
2.4  10
s
–21
1.9  10
s
–5
6.3  10 s
6. An electron in a hydrogen atom makes a transition from the n = 4 to the n = 3 energy state. Determine the energy (in eV) of
the emitted photon.
a.
0.54
b.
0.66
c.
0.85
d.
1.51
e.
10.2
7. An electron with kinetic energy 2.80 eV encounters a potential barrier of height 4.70 eV. If the barrier width is 0.40 nm, what is
the probability that the electron will tunnel through the barrier?
A) 3.5 × 10-3
B) 7.3 × 10-3
C) 1.4 × 10-2
D) 2.9 × 10-3
E) 3.5 × 10-2
8. The lowest energy level of a certain quantum harmonic oscillator is 5.00 eV. What is the energy of the next higher level?
A) 7.50 eV
B) 10.0 eV
C) 15.0 eV
D) 20.0 eV
E) 50.0 eV
9. The probability density for an electron that has passed through an experimental apparatus is given in the figure. The probability
is symmetric about x = 0 (that is P(-x) = P(x)). The second peak is not drawn to scale, but you can figure out its height from the
normalization of P(x). What is the probability that the electron will land in a 0.10 mm-wide strip at
x = 2.000 mm?
A) 0.0026
B) 0.0032
C) 0.0037
D) 0.0042
10. The wave function for an electron that is confined to x ≥ 0 nm is ψ(x) =
What is the probability of finding the electron in the interval 1.15 nm ≤ x ≤ 1.84 nm?
A) 0.17
B) 0.16
C) 0.80
D) 0.33
11. A particle is confined to a one-dimensional box (an infinite well) on the x-axis between x = 0 and x = L. The potential height
of the walls of the box is infinite. The normalized wave function of the particle, which is in the ground state, is given by
ψ(x) =
sin
, with 0 ≤ x ≤ L. What is the probability of finding the particle between x = 0 and x = L/3?
A) 0.20
B) 0.22
C) 0.24
D) 0.26
E) 0.28
12. The normalized wave function for a hydrogen atom in the 1s state is given by ψ(r) =
e-r/α0 where α0 is the Bohr
radius, which is equal to 5.29 × 10-11 m. What is the probability of finding the electron at a distance greater than 7.8 α0 from the
proton?
A) 2.3 × 10-5
B) 1.2 × 10-5
C) 1.7 × 10-5
D) 4.6 × 10-5
E) 3.5 × 10-5
13. About how many days are required for a radioactive sample, with an initial activity of 105 Bq, to decay to an activity of 100
Bq? The half-life of the material is 5.7 days.
A) About 57 days
B) About 46 days
C) About 68 days
D) About 39 days
14. An archaeologist finds the 14C in a sample of 3.10 g of material to be decaying at 107 counts per second. A
modern 1.00-g sample of the same material decays at 151 counts per second. The half-life of 14C is 5730 years. How
old is the sample?
A) 12,200 years
B) 8460 years
C) 25,100 years
D) 12,600 years
15. The neutral
Al atom has a mass of 26.981539 u; a neutral hydrogen atom has a mass of 1.007825 u; a
neutron has a mass of 1.008665 u; and a proton has a mass of 1.007277 u. What is the binding
energy per nucleon for Al? (1 u = 931.5 MeV/c2)
A) 8.3 MeV
B) 6.7 MeV
C) 5.4 MeV
D) 3.4 MeV
E) 2.8 MeV
The BIO FX Problem
Uranium-238 decays into thorium-234 plus an alpha particle. The relevant atomic mass values are
He:
4.002603 u
Th:
234.043583 u
U:
238.050786 u
a. Write out the decay equation and calculate how much energy is released.
b. An unlucky miner accidently eats a microgram of U-238. What is consequences due to the ionizing radiation?
Calculate the rem for acute exposure and use the UN tables to discuss risk.
c. What are the long term effects? Discuss not only the latent effects due to Uranium decay but also how uranium
behaves chemically and how that impacts the body. Do not ignore the daughter products in this discussion.