Edexcel GCSE Combined Science CP4 and CP5 Waves and the electromagnetic spectrum: a complete overview of wave properties, the wave equation and EM radiation

What CP4 and CP5 actually demand

Waves and the electromagnetic spectrum, on Physics Paper 1, combine a calculation thread (the wave equation) with a recall thread (the EM spectrum and its uses). The examiners reward correct use of the wave equation, the order of the spectrum, and the uses and dangers of each type of radiation.

This guide walks through both topics and ties together the matching dot-point pages, each with its own practice questions.

Wave properties

A wave transfers energy without matter. Transverse waves oscillate perpendicular to travel (light); longitudinal waves oscillate parallel to travel (sound). The wave quantities are amplitude, wavelength, frequency (in hertz) and period, with $T = \frac{1}{f}$. The wave equation is:

At a boundary, waves can be reflected (bounce back) or refracted (change direction as their speed changes).

The electromagnetic spectrum

The EM spectrum is a family of transverse waves travelling at the speed of light in a vacuum. In order of increasing frequency: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Each has uses (broadcasting, cooking and communication, heating, sight, security, medical imaging and treatment), and the higher-energy waves (ultraviolet, X-rays, gamma) can damage cells and cause cancer.

How CP4 and CP5 are examined

• Calculations. Using and rearranging the wave equation.
• Wave types. Distinguishing transverse and longitudinal waves.
• The spectrum. Listing the order and the inverse wavelength-frequency relationship.
• Uses and dangers. Matching each radiation to its uses and stating the dangers.

Check your knowledge

A mix of recall and calculation questions covering CP4 and CP5. Attempt them under timed conditions, then check against the solutions.

1. State the difference between a transverse and a longitudinal wave. (2 marks)
2. Define the frequency of a wave. (1 mark)
3. Write the wave equation. (1 mark)
4. A wave has frequency 5 Hz and wavelength 3 m. Calculate its speed. (2 marks)
5. What happens to a wave when it is reflected? (1 mark)
6. List the EM spectrum from longest to shortest wavelength. (2 marks)
7. Give one use of microwaves. (1 mark)
8. State one danger of ultraviolet radiation. (1 mark)