PHYS 3310 Module 3.2

Photoelectric Effect

Recommended Reading

3.2 Photoelectric Effect

Learning Objectives

  • Describe physical characteristics of the photoelectric effect
  • Explain why the photoelectric effect cannot be explained by classical physics
  • Describe how Einstein’s idea of a particle of radiation explains the photoelectric effect
Practice 3.2.1

The battery voltage is 5 V.  What is the potential difference between A (the emitter) and B (the collector)?
A. 0 V
B. 5 v
C. 50 V
D. impossible to determine
Check your answer: B. 5 V
Practice 3.2.2

What is the direction of the Electric Field between A and B?
A. to the right, from A to B
B. to the left, from B to A
C. E = 0 between A and B
D. impossible to determine
Check your answer: B. to the left, from B to A
Practice 3.2.3

What would happen if you placed a free electron near A?
A. the electron would move at a constant speed from A to B
B. the electron would accelerate from A to B
C. the electron would remain at rest at A
D. impossible to determine
Check your answer: B. the electron would accelerate from A to B
Practice 3.2.4

How much kinetic energy will the free electron have when it gets to B?
A. 0 eV
B. 5 eV
C. 50 eV
D. impossible to determine
Check your answer: B. 5 eV
Practice 3.2.5

Remove the free electron. The potential difference between A and B is 5 V and the resistor has 10 ohms of resistance. What is the current from A to B?
A. 0 A
B. 5 A
C. 50 A
D. 0.5 A
E. impossible to determine
Check your answer: A. 0 A
Practice 3.2.6

Heat up plate A until it’s just hot enough to barely “burn off” some electrons. (This is called thermionic emission.) What will a graph of current vs. voltage look like?
A.
B.
C.
D.
E. something else
Check your answer: C

Photoelectric Effect Experiment, Part 1

Practice 3.2.7
Which graph represents low (purple) and high (orange) intensity curves?
A.
B.
C.
D.
E.
Check your answer: B

Photoelectric Effect Experiment, Part 2

Practice 3.2.8
Which graph represents longer (purple) and shorter (orange) wavelengths?
A.
B.
C.
D.
E.
Check your answer: D

Photoelectric Effect Experiment, Part 3

Practice 3.2.9

Which metal (A or B) has the larger work function?
A. metal A
B. metal B
C. the two metals have the same work function
D. impossible to determine
Check your answer: B
Practice 3.2.10
Which of the following energy diagrams correctly describes the photoelectric effect? (Eb is the binding energy, or the work function)
A.
B.
C.
Check your answer: A