1. Light has a wavelength of 3.86 X 10-9 m. How much energy does a photon have?
(4 marks)
2. Light of wavelength 438 nm is directed at a metallic surface. The emitted photoelectrons are
stopped by an electric potential of 0.530 V.
a) What is the maximum speed of the photoelectrons? (2 marks)
b) What is the threshold frequency for the metal? (3 marks)
3. A photon has an energy of 2.73 X 103 eV. What is the momentum of the photon?
(4 marks)
4. A stationary electron is hit by a photon which has an energy of 4.31 X 10-19 J. If the photon
loses 0.898 eV of energy, what is the change in momentum of the photon? (6 marks)
5. An alpha particle (a helium nucleus) has a mass of 6.65 X 10-27 kg. The particle is accelerated
through a potential difference of 225 V. What is the de Broglie wavelength of the particle?
(3 marks)
6. A 73.2 kg person has a de Broglie wavelength of 4..09 X 10-37 m. What is the person's
speed? (3 marks)
7. Atoms are bombarded by electrons which have an energy of 1.59 X 10-18 J. This causes the
atoms to jump from ground state to their first and second excitation levels of 3.3 eV and
5.0 eV. What are the energies of the incident electrons after interaction? (3 marks)
8. Atoms are bombarded by photons. This causes these atoms to move from ground state to the
first excitation state of 4.36 eV. What is the momentum of the photons? (3 marks)
9. An electron of energy 1.36 X 10-19 J is incident upon a hydrogen atom. This causes an
electron to jump from the third to the fourth energy level.
a) What is the final energy of the incident electron? (3 marks)
b) What wavelength of light is emitted if the electron drops from the fourth level to the
second level? (2 marks)
10. What is the speed of an electron that is in the third Bohr orbit of a hydrogen atom?
(3 marks)
11. The uncertainty in position of an electron is 3.61 X 10-12 m. What is the uncertainty in its
speed? (3 marks)
January 20, 2014