AQA AS Level Physics Paper 2, June 2023: Question 13

1 mark · Medium difficulty · Multiple Choice

Determine the effect of increasing the frequency of incident monochromatic light, while keeping the photon arrival rate constant, on the photoelectric current and the magnitude of the stopping potential.

Practise this question

Question

Multiple choice question 13 asking how the photoelectric current and magnitude of stopping potential change when the frequency f of monochromatic light is increased without changing the rate at which photons arrive. A table presents four options (A, B, C, D) with various combinations of current (I or > I) and stopping potential (Vs or > Vs).
Question text

13 Monochromatic light of frequency f is incident on a metal surface in a vacuum.

Photoelectrons are emitted from the surface.

The photoelectric current I is measured.

The magnitude of the stopping potential Vs is then measured.

f is increased without changing the rate at which photons arrive at the metal surface.

What are the new measurements of the photoelectric current and the magnitude of the

stopping potential?

[1 mark]

Photoelectric current Magnitude of the stopping potential

A I Vs

B I > Vs

C > I Vs

D > I > Vs

Mark scheme

Show the mark scheme Mark scheme showing the correct answer for question 13 is option B, indicating the photoelectric current remains I and the magnitude of the stopping potential becomes greater than Vs.

13 B I > Vs

How to answer it

Effect of Frequency Changes on Photoelectric Current and Stopping Potential

What this question tests:
This question tests your understanding of the photoelectric equation, specifically how changing the frequency of incident photons affects maximum kinetic energy (and therefore the stopping potential), and how photon rate relates to photoelectric current.
Question 13

Exam Breakdown & Solution

✅ Correct Answer: Option B

Photoelectric current = I
Magnitude of stopping potential = > Vₛ

💡 Key Knowledge

  • Photoelectric Current ( I ): Depends strictly on the rate at which photons hit the metal surface (intensity), not their frequency. Since the photon arrival rate is unchanged, the current remains I .
  • Stopping Potential ( Vₛ ): Governed by Einstein's photoelectric equation: e Vₛ = hf - φ . Increasing frequency ( f ) increases the maximum kinetic energy of emitted photoelectrons, requiring a larger stopping potential to halt them.

🧠 Exam Technique

Tackle multi-variable multiple-choice questions by analyzing variables independently. First, lock down what happens to the current when intensity is constant (eliminates options C and D). Second, evaluate the energy relationship to determine the direction of change for the stopping potential.

❌ Common Errors

A frequent misconception is thinking that increasing the frequency of light also increases the current because the photons are "more energetic." Remember that one photon interacts with one electron; current depends on the number of electrons liberated per second, not their individual energies.

Mark Scheme Allocation: 1 mark awarded for selecting option B.

Topics

Physics · 3.2 Particles and radiation

Question and mark scheme from the AQA AS Level Physics examination, Paper 2, June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.