Particle and Quantum Physics

Question 1

Give three observations of the photoelectric effect that challenged the wave theory of light.

Answer 1

1. The emission of photoelectrons is instantaneous and indpendent of intensity.
2. There’s a threshold frequency, below which no emission can be observed.
3. The KE of the photoelectrons is purely dependent on the frequency, not the intensity.

Question 2

Work function of a metal

Answer 2

The energy required by an electron to be released from the surface of the metal.

Question 3

Stopping potential

Answer 3

The minimum potential difference across a cathode and anode that only just stops photoelectrons from reaching the anode (due to the electric field doing work to decelerate the photoelectrons).

Question 4

Copenhagen Intepretation

Answer 4

When a measurement is taken the wavefunction collapses, so the probability
(∝ |wavefunction|^2) goes to 1 at the point where the wavefunction collapses to. Prior to this detection, the wavefunction is a superposition of all the states where the electrons could be.