Practice Problems for the Photon Model of Light


For additional practice, there are also some nice simulations which may help you to improve your qualitative understanding of some topics.

Photoelectric effect:
1. In the photoelectric effect,
  When the frequency of the incident light is increased,
the number of released photons _________
the energy of the released photons ______________
the time between turning on the light and observing the photoelectric current __________
  When the brightness of the incident light is decreased,
the number of released photons _________
the energy of the released photons ______________
the time between turning on the light and observing the photoelectric current __________
 
2. Explain how the wave model of light fails to explain the following, requiring the photon model of light to account for the observed behavior.

a. the existence of a cutoff frequency, below which no electrons are ejected.
 
 
b. the nearly instantaneous ejection of electrons, as long as the incident light is above the cutoff frequency, even at extremely low intensities.
 
 
c. the lack of influence of incident brightness on the energy of the ejected electrons.
 
 
 
3. In the photoelectric effect, the work function of nickel is 5.01 eV. Determine the cutoff frequency for nickel.

Solutions to Photoelectric effect problems


Bohr model of the atom and spectra
1. Look back at the end of worksheet 3 for your calculations of the energy levels of hydrogen from n=1 to n=5.

a. Make an energy level diagram for hydrogen.
b. On the diagram, draw all of the transitions that can occur between those energy levels and label the transition energies.
c. Which of the transitions will produce light in the visible spectrum?
d. Which transition will produce photons of the greatest energy?
e. Which transition will produce photons of the greatest wavelength?

Solutions to Bohr model of the atom questions


The wave-particle nature of light
1. How many 3.0 eV purple photons are needed to equal the energy of a 10e-5 nm wavelength gamma ray photon?
 
2. The pen lasers we used in class have an output of 5 mW at a wavelength of 670 nm. How many photons emerge from the laser pointer each second?

Solutions to wave particle questions