IGCSE Physics: Waves, Light and Sound

Waves is a topic where IGCSE Physics students either shine or crash — the difference is precision of language. The mark scheme rewards specific terms ("bends towards the normal", "diffracts through the gap") and penalises everyday phrasing. This hub sharpens the vocabulary and the diagrams you'll be asked to draw.

Practice this topic by speaking your answer

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What you need to master

1General wave properties: wavelength, frequency, amplitude, period, wave speed.
2Transverse vs longitudinal waves with examples (light vs sound).
3Reflection, refraction, diffraction and their diagrams.
4Snell's law, critical angle and total internal reflection.
5The electromagnetic spectrum: order, uses and dangers.
6Sound waves: speed, pitch, loudness and hearing range.
7Lenses: converging, diverging, and ray diagrams for image formation.

Key formulas

v = fλ

T = 1/f

n = sin(i)/sin(r)

n = 1/sin(c) (critical angle)

Examiner tips

•When describing refraction, always mention "bends towards/away from the normal" AND "slows down/speeds up because it enters a denser/less dense medium".
•Draw refraction diagrams with a clearly labelled normal (dashed line) — missing this drops marks.
•State the order of the EM spectrum from memory; questions often hide it in a "state the three missing regions" format.

Common mistakes to avoid

•Saying "light bends because the glass is thicker" — the correct reason is optical density, not thickness.
•Mixing up frequency and wavelength when pitch is asked.
•Drawing refracted rays on the wrong side of the normal.