AQA A-Level Physics Paper 1, June 2024: Question 13

1 mark · Medium difficulty · Multiple Choice

Calculate the number of complete waves emitted by a laser with a wavelength of 600 nm operating for 10 ns.

Practise this question

Question

Multiple choice question 13 showing text: 'A laser emits light of wavelength 600 nm for 10 ns. What is the number of complete waves emitted by the laser?' followed by four options A, B, C, and D with respective numerical values and boxes.
Question text

13 A laser emits light of wavelength 600 nm for 10 ns.

What is the number of complete waves emitted by the laser?

[1 mark]

A 5 × 1017

B 5 × 1012

C 5 × 108

D 5 × 106

Mark scheme

Show the mark scheme Mark scheme table showing question number 13 with the correct answer D and the value 5 times 10 to the power 6.

13 D 5 × 106 AO2

How to answer it

Laser Wave Emission Calculation

📌 What this question tests

This question assesses your ability to apply fundamental wave equations ( c = f × lambda ), convert standard metric prefixes (nanometres and nanoseconds), and calculate the total number of complete cycles emitted over a given time interval. It targets AO2 (Application).

Question 1.3

A-Level Physics Multiple Choice Question

✅ Correct Answer

D ( 5 × 10⁶ )

1 mark available for selecting the correct option.

💡 Key Knowledge

  • The wave speed equation: c = f × lambda , where c is the speed of light in a vacuum ( 3 × 10⁸ m s⁻¹ ).
  • Frequency f represents the number of waves passing a point per second.
  • Prefix conversions: nano means × 10⁻⁹ .

🧠 Exam Technique

Break the problem down into two clear stages: first find the frequency of the light, then multiply by the total time duration. Always write down your unit conversions before plugging numbers into your calculator to avoid power-of-ten errors.

❌ Common Errors

  • Forgetting to convert nanometres ( nm ) and nanoseconds ( ns ) into base SI units.
  • Dividing time by frequency instead of multiplying by total time.
  • Inverting the wave equation ( f = lambda / c instead of c / lambda ).

📐 Step-by-Step Calculation

  1. Identify known variables:
    Wavelength ( lambda ) = 600 nm = 600 × 10⁻⁹ m
    Time duration ( t ) = 10 ns = 10 × 10⁻⁹ s
    Speed of light ( c ) = 3 × 10⁸ m s⁻¹
  2. Calculate the frequency ( f ):
     f = c / lambda
    f = (3 × 10⁸) / (600 × 10⁻⁹) = 5.0 × 10¹⁴ Hz
  3. Calculate the total number of complete waves:
    Number of waves = Frequency × Time ( f × t )
    Number of waves = (5.0 × 10¹⁴ Hz) × (10 × 10⁻⁹ s)
    Number of waves = 5 × 10⁶

Topics

Physics · 3.3 Waves

Question and mark scheme from the AQA A-Level Physics examination, Paper 1, June 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.