Pearson Edexcel International GCSE
Physics — Topic 3 Paper 3
Waves · specification 3.1–3.23
Time allowed: 30 minutes
Total marks: 25
Candidate name:
Centre / class:
Answer all questions. You may use a calculator. Show your working. Take the speed of sound in air as $340\,\text{m/s}$.
1
A loudspeaker at a swimming pool produces a note of frequency $680\,\text{Hz}$.
(a) Sound is a longitudinal wave. Describe what this means, and name the two regions that repeat along a sound wave.
[3]
(b) Calculate the wavelength of the sound in air.
[2]
(c) A swimmer moves towards the loudspeaker. State what happens to the frequency she hears. Name the effect.
[1]
(Total for Question 1 = 6 marks)
2
A ray of light in air hits the surface of the pool. $i=50^\circ$ and $r=31^\circ$.
(a) State whether the light speeds up or slows down as it enters the water, and whether it bends towards or away from the normal.
[2]
(b) Calculate the refractive index of the water.
[2]
(c) Take $n=1.33$ for water. Calculate the critical angle for a water–air boundary.
[3]
(Total for Question 2 = 7 marks)
3
X-rays are used to check a swimmer’s broken wrist. A 45° glass prism can turn a light ray through $90^\circ$ by total internal reflection.
(a) State one specification use of X-rays other than medical imaging.
[1]
(b) Explain why a 45° prism can use TIR if glass has $c \approx 42^\circ$.
[2]
(c) Gamma rays are used to sterilise medical equipment. State one detrimental effect of gamma rays and one protective measure.
[3]
(Total for Question 3 = 6 marks)
4
A student measures $i$ and $r$ for a glass block.
| $i$ / ° | 20 | 30 | 40 | 50 |
|---|---|---|---|---|
| $r$ / ° | 13 | 19 | 25 | 40 |
(a) Calculate $n$ using the $40^\circ$ pair of results.
[2]
(b) Identify the anomalous pair and suggest one practical reason for it.
[2]
(c) State how the student should use the remaining results to give a better value of $n$.
[2]
(Total for Question 4 = 6 marks)
END OF PAPER 3