Chapter 27 – 30 Homework Problems
Ch27 HW#1 1 – 5
1. How much energy is associated with blue light that has a frequency of 6.3 x 10 14 Hz?
2. How much energy is associated with a radio wave of wavelength 1 meter?
3. How much energy is associated with an X-ray of wavelength 1 x 10-10 m?
4. The threshold wavelength of zinc is 310 nm.
a. Find the threshold frequency of zinc.
b. What is the work function of zinc?
c. Zinc in a photocell is irradiated by ultraviolet light of 240 nm wavelength.
What is the kinetic energy of the photoelectrons?
5. The work function for cesium is 1.96 eV.
a. Find the threshold wavelength for cesium. (First convert eV to Joules)
b. What is the kinetic energy of photoelectrons ejected when 425-nm violet light falls on the cesium?
Ch27 HW#2 6 – 9
6. Mr Purser of mass 75 kg is walking around the class at a speed of 1 m/s. Calculate his de Broglie wavelength.
7. An electron of mass 9.11 x 10-31 kg is accelerated by a potential difference up to a speed of 4.3 x 10 6 m/s.
What is the de Broglie wavelength of this electron?
8. A 7.0-kg bowling ball rolls with a velocity of 8.5 m/s.
a. What is the de Broglie wavelength of the bowling ball?
b. Why does the bowling ball exhibit no observable wave behavior?
9. An X ray with a wavelength 5.0 x 10-12 m is traveling in a vacuum.
a. Calculate the mass associated with this X ray. (Hint: v = c)
b. Why does the X ray exhibit little particle behavior?
Ch28 HW#1 1 – 5
1. The diameter of the hydrogen nucleus is 2.5 x 10 -15 m and the distance between the nucleus and the first electron
is about 5 x 10-9 m. If you use a baseball with diameter of 7.5 cm to represent the nucleus,
how far away would the electron be?
2. A mercury atom drops from 8.82 eV to 6.67 eV.
a. What is the energy of the photon emitted by the mercury atom?
b. What is the frequency of the photon emitted by the mercury atom?
c. What is the wavelength of the photon emitted by the mercury atom?
3. The electron in a hydrogen atom drops from 11.6 eV to 5.1 eV.
a. What is the energy of the photon emitted by the electron?
b. What is the frequency of the photon emitted by the electron?
c. What is the wavelength of the photon emitted by the electron?
4. An electron in a sodium atom absorbs a photon and then re-emits a photon as it returns to its base state.
The photon emitted has the wavelength of orange light, 600 nm.
a. What is the frequency of the emitted photon?
b. What is the energy of the emitted photon?
5. An electron in a copper atom absorbs a photon and then re-emits a photon as it returns to its base state.
The photon emitted has the wavelength of blue-green light, 490 nm.
a. What is the frequency of the emitted photon?
b. What is the energy of the emitted photon?
Ch30 HW#1 1 – 6
1. Three isotopes of uranium have mass numbers of 234, 235, and 238. The atomic number of uranium is 92.
How many neutrons are in the nuclei of each of these isotopes?
2. An isotope of oxygen has a mass number of 15. How many neutrons are in the nuclei of this isotope?
3. How many neutrons are in the mercury isotope 20080 Hg?
4. Write the symbols for the three isotopes of hydrogen, which have zero, one, and two neutrons in the nucleus.
5.
Write the nuclear equation for a radioactive uranium isotope,
and an alpha particle,
6.
.
Write the nuclear equation for a radioactive thorium isotope,
and an

234
92
U , decaying into a thorium isotope
230
90
Th, decaying into a radioactive radium isotope
particle.
Ch30 HW#2 7 – 13
7.
Write the nuclear equation for the transmutation of a radioactive radium isotope,
8.
into a radon isotope and an  particle.
Please find the missing particle in each nuclear equation
b.
1
9
4
4 Be + 2 α  ___ + 0 n
210
4
84 Po  ___ + 2 α
c.
10
5B
a.
9.
+
4
2
226
88
Ra,
1
He  ___ + 0 n
3
A sample of 1.0 g of tritium , 1 H, is present. (Half Life of 12.3 years.)
What will be the mass of the tritium remaining after 24.6 years?
10. The isotope
238
93 Np
has a half-life of 2.0 days. If 4.0 g of neptunium is produced Monday,
what will the mass of neptunium remaining on Tuesday of the next week?
11. If Mr. P weighs 75 kg, and his entire mass could be converted into energy to power up the high desert,
how much energy is associated with this amount of mass?
If the Hi Dez uses ~ 50,000 Watts (Joules per second), how long could I power the Hi Dez?
12. In an experiment at Lawrence Livermore Research Facility, it was found that in the radioactive decay
of Uranium into Thorium, a little bit of mass disappeared. (It converted into energy.)
They call this the mass defect. If a basketball size piece of uranium forms a chain reaction,
and the mass defect is 1 kg, how much energy is produced?
13. The mass of a proton is 1.67 x 10-27 kg. Find the energy associated with this mass.
Relativity Questions
1. If 1 year passes for you in your spaceship traveling at 99.9% c,
how much time passes for me stuck here on earth?
2. If you hold a meter stick out the window of your rocket ship while traveling at 85% c,
how long will I observe it to be when you zoom by the earth?
3. How heavy does a 1 kg mass become if someone accelerates it up to 99.9% c
while they are stationary?