Pearson Edexcel International GCSE
Physics — Topic 3 Paper 1
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 electromagnetic waves in free space as $3.0 \times 10^8\,\text{m/s}$.
1
A student watches ripples on a pond. The frequency of the ripples is $2.5\,\text{Hz}$ and the wavelength is $12\,\text{cm}$.
(a) State whether water ripples are transverse or longitudinal. Explain your answer.
[2]
(b) Calculate the speed of the ripples.
[3]
(c) State the time period of the ripples.
[1]
(Total for Question 1 = 6 marks)
2
A ray of light in air hits a rectangular glass block. The angle of incidence is $42^\circ$ and the angle of refraction in the glass is $26^\circ$.
(a) State the law of reflection.
[1]
(b) Calculate the refractive index of the glass.
[3]
(c) Another sample of glass has $n=1.50$. Calculate the critical angle for a glass–air boundary.
[3]
(Total for Question 2 = 7 marks)
3
Ultraviolet radiation is part of the electromagnetic spectrum. A dentist uses an optical fibre to send visible light into a patient’s mouth.
(a) Name the EM band with a longer wavelength than ultraviolet and the band with a shorter wavelength than ultraviolet, using neighbours in the spectrum.
[2]
(b) Explain how total internal reflection allows light to travel along the optical fibre.
[2]
(c) State one detrimental effect of excessive ultraviolet exposure and one protective measure.
[2]
(Total for Question 3 = 6 marks)
4
A student investigates the refractive index of a rectangular glass block.
(a) Describe a method the student should use to obtain values of $i$ and $r$. Include how the student draws the normal.
[4]
(b) Suggest two ways the student could reduce the uncertainty in $n$.
[2]
(Total for Question 4 = 6 marks)
END OF PAPER 1