Module 4 - 4.5.2 The Photoelectric Effect

Question 1

The Photoelectric Effect (red light)

Answer 1

Red light photons don’t have enough energy to overcome the energy needed to release an electron

Question 2

The Photoelectric Effect (ultraviolet light)

Answer 2

The electron absorbs the photon’s energy and is released from the atom
(the left over energy is converted into kinetic energy of the photoelectron)

Question 3

Photon - Electron Relationship

Answer 3

One to One
A single photon can only eject one electron from a surface

Question 4

The Work Function

Answer 4

The minimum amount of energy an electron needs to be released from the atom

Question 5

The Threshold Frequency

Answer 5

The minimum frequency required to release an electron

Question 6

Rate of Emission and Intensity

Answer 6

Rate of emission of photoelectrons (above threshold frequency) is directly proportional to the intensity of the incident radiation

Question 7

The Gold Leaf Experiment (5)

Answer 7

• regardless of intensity, nothing happens if red light is shone at the zinc plate
• if UV light is shone at the zinc plate
• • causes the surface electrons on the plate to deflect
• • this removes the charge on the gold leaf causing it to fall
• • works even at low intensities

Question 8

The Gold Leaf Experiment (Conclusion)

Answer 8

The changing the intensity effect cannot be explained by a wave model and so led to thinking of light as a particle