1. Electrons are used to bombard a sample of a metallic element in a gaseous form. The energies
of the electrons is increased over time with the following results.
a) When the electrons have less than 1.4 eV, the electrons do not seem to lose any energy.
b) When the electrons have kinetic energies of 2.1 eV, they seem to lose energy and retain
0.6 eV.
c) Electrons which had 5.7 eV of kinetic energy, scatter and retain 4.2 eV or 2.4 eV of
kinetic energy.
Determine the most likely energies for the first two energy levels for this element.
2. Using the data discussed in class for the Franck-Hertz experiment, draw an energy level
diagram for mercury.
3. Electrons are colliding with gaseous mercury atoms. If the initial kinetic energy of the electrons
is 3.9 eV, what will be there kinetic energy after collision?
4. Electrons are accelerated through a potential difference 0f 7.0 V. These electrons then interact
with mercury vapour. Calculate the energies of all the photons emitted by the mercury.
5. A photon has an energy of 150 eV. What is its momentum?
6. An electron is moving at 1.0 X 106 m/s. What would be the wavelength of a photon with the
same momentum?
7. a) A photon has a wavelength of 2.0 X 10-7 m. What is its frequency?
b) For this same photon, determine its energy. Express your answer in both electron volts
and Joules.
c) Calculate the momentum of this photon.
8. A photon has a wavelength of 0.20 nm. What is its equivalent mass and momentum?
9. For each of the following situations, determine the wavelength of the matter waves.
a) A ball of mass 2.0 kg, is thrown with speed 15 m/s.
b) A proton of mass 1.67 X 10-27 kg is accelerated through a potential difference so that
its speed is 1.3 X 105 m/s.
c) An electron has been accelerated through a potential difference to give it a speed of
5.0 X 104 m/s.
10. Determine the de Broglie wavelength for an electron with kinetic energy of:
a) 3.0 eV b) 5.0 eV
11. Scientists wanted an electron to have a de Broglie wavelength of 0.15 nm. What would be
the energy of this electron? Express your answer in electron volts.
12. A student accelerates an electron through a potential difference of 100 V. What would be
this student's calculation for the de Broglie wavelength for this electron?
13. The velocity of the electron in the first Bohr orbit of hydrogen is 2.19 X 106 m/s.
a) Determine the de Broglie wavelength for an electron in the first Bohr orbit of hydrogen.
b) Compare the de Broglie wavelength for an electron in the first Bohr orbit of hydrogen,
to the circumference of this first Bohr orbit.
14. During fluorescence, the wavelength of the emitted light is the same or longer than the light
which was absorbed by the fluorescing material. Explain this observation.
15. The emission lines in the Balmer series for hydrogen are produced when electrons move from
higher energy levels to the second energy level. Calculate the wavelength for the Balmer
series line for which n = 4.
16. What is the ratio of the gravitational force to the electrical force between an electron and
proton in ground state for a hydrogen atom? Given your calculated ratio, can either of these
two forces be ignored?
17. How much larger is the volume of a hydrogen atom when in its first excited state, compared to
its ground state? You may assume that the shape of the hydrogen atom is a sphere.
18. From what you have learned about the energy levels of hydrogen, determine the wavelengths
of the emitted light, when electrons which have been accelerated through a potential difference
of 12.3 V, pass through hydrogen gas.
19. If hydrogen is in the first excited state, how much energy is needed to ionize the atom? What
are the chances of this ionization occurring? Explain.
20. Hydrogen gas is emitting light of wavelength 388 nm. What are the quantum numbers for the
energy levels responsible for this emission?
21. A sample of hydrogen has been raised to the n = 5 excited state. What are the energies of all
the photons that could possibly be emitted from this sample?
22. For a hydrogen atom, if an electron was in an orbit of radius 1.0 mm, what would be the
quantum number for the orbit? Calculate the energy of this orbit.
23. Gamma rays and X-rays both are fairly high energy electromagnetic waves. What are their
differences?
24. Alpha and beta rays are two types of radiation given off during radioactive decay. If these
two types of radiation have the same speed, and they both pass through the same uniform
magnetic field,
a) which of these particles would experience the greater force?
b) which of these particles would have the smallest radius for its path?
25. For each of the following circumstances, what type of radioactive detector could be used?
a) Scientists want to detect the presence of alpha particles.
b) Scientists want to detect gamma radiation from a radioactive source.
c) A researcher wants to determine the direction of motion of a particle.
d) A health physicist wants to find how far a radioactive particle penetrates into a
radiation shield.
e) An atomic physicist wants to detect the collision between two particles.
26. What is the activity for each of the following sources?
a) The sources produces 100 000 emissions in 1.0 s
b) During a 30 s time period, the source produces 4.8 X 106 emissions.
c) A total of 3.2 X 103 particles are emitted from the source in 1.2 min.
27. Radio active chemicals are often used in diagnostic tests run on patients. If a radioactive
chemical used in a kidney test has an activity of 7.0 MBq, in 2.0 min, how many emissions
would be counted. You may assume that the chemical concentrates in the kidney.
January 20, 2014