10 minutes maximum! Can you do it in 5?

1. The photoelectric effect demonstrates..

• A. The wave properties of photons and electrons.
• B. The particle properties of photons and the wave properties of electrons.
• C. The wave properties of photons and the particle properties of electrons.
• D. The particle properties of photons and electrons.

2. The work function Φ of a metal is defined as:

• A. The frequency of a photon required to liberate an electron from the metal.
• B. The energy required to liberate an electron from the metal.
• C. The momentum given to an electron liberated from the metal.
• D. The kinetic energy given to an electron liberated from the metal.

3-5. The graph below shows how the maximum kinetic energy Emax of the electrons varies with the frequency of the incident light on a clean metal surface. 3. What is the gradient of this graph?

• A. hf
• B. -Φ
• C. Φ
• D. h

4. What is equal to the Y intercept of this graph?

• A. hf
• B. -Φ
• C. Φ
• D. h
5. Which of the following quantities is equal to the threshold frequency? 6. Light of wavelength λ is incident on a clean metal sheet, and photoelectrons are liberated with minimal kinetic energy. Which of the following will changes will prevent photoelectrons from being emitted?

• A. Increase the energy of the incident photons
• B. Increase the wavelength of the incident light.
• C. Use a metal sheet with a lower work function.
• D. Decrease the power output of the light source.

7. Photoelectrons of maximum kinetic energy E are liberated from a metal sheet of work function Φ when photons of frequency f are incident on the metal.
What is the maximum kinetic energy of the photoelectrons if a new metal of work function 2Φ is used, and the frequency of light is also doubled?

• A. ½E
• B. E
• C. 2E
• D. 4E

8. Photoelectrons liberated from a metal can produce a current I in an external circuit. The number of photons incident on the sheet is kept constant whilst the frequency f is varied. Which of the following graphs best shows how I varies with f? 9. The kinetic energy of the photoelectrons can be found by applying a stopping potential.
If the work function of the metal is 2.8 eV, and the value of 'hf' is 5.7 eV, then the stopping potential is:

• A. 2.9 eV
• B. 2.9 V
• C. 8.5 eV
• D. 8.5 V
10. A red 60W lamp is used to produce a small current I from a photocell, with a stopping potential of V. The red lamp is replaced with a violet lamp of the same power output. What effect does this have on I and V?
 I V A decreases decreases B no effect decreases C decreases increases D no effect increases