AQA AS Level Physics Paper 2, June 2023: Question 25

1 mark · Medium difficulty · Multiple Choice

Identify the combination of changes to wavelength and slit width that will always produce a wider central diffraction maximum for monochromatic light passing through a single slit.

Practise this question

Question

Multiple choice question 25 asks to identify the combination of changes to wavelength lambda and slit width s that will always produce a wider central diffraction maximum. A table lists four options (A to D) with changes to lambda (decrease or increase) and changes to s (decrease or increase).
Question text

25 A central diffraction maximum is observed when monochromatic light of wavelength λ

passes through a single slit of width s.

Which combination of changes to λ and s will always produce a wider central diffraction

maximum?

[1 mark]

Change to λ Change to s

A decrease decrease

B decrease increase

C increase decrease

D increase increase

Mark scheme

Show the mark scheme Mark scheme indicating the correct answer is C, corresponding to an increase in wavelength and a decrease in slit width.

25 C increase decrease

How to answer it

Single Slit Diffraction Pattern Width

What this question tests

This question assesses your understanding of single slit diffraction physics, specifically how changing the wavelength of incident light (λ) and the slit width (s) affects the angular or linear width of the central diffraction maximum.

Question 25 [1 mark]

Exam Breakdown & Solution

✅ Correct Answer: C

Change to λ: increase
Change to s: decrease

💡 Key Knowledge

  • The angular width of the central diffraction maximum is proportional to λ / s .
  • Increasing the wavelength ( λ ) spreads out the diffraction pattern, making the central maximum wider.
  • Decreasing the slit width ( s ) increases the degree of diffraction, also making the central maximum wider.

🧠 Exam Technique

For multiple-choice proportionality questions, write out the relevant equation first. Here, recall that angular half-width θ ≈ λ / s, meaning the overall width of the central maximum depends directly on λ and inversely on s.

❌ Common Errors

Students sometimes confuse single-slit diffraction formulas with double-slit interference fringe spacing formulas (where fringe width is proportional to slit separation w = λD / s ). Always double-check whether you are dealing with diffraction patterns or interference fringes.

Examiner Guidance: This is a straightforward recall and proportionality check. Option C correctly identifies that increasing the numerator ( λ ) and decreasing the denominator ( s ) will both independently work to increase the overall value, maximizing the central width.

Topics

Physics · 3.3 Waves

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.