← Waves

Reading the notation

A small set of symbols carries every part of this paper — get them precise, since a mixed-up n₁/n₂ or a wrongly-placed image is the fastest way to lose a method mark.

📖 Symbols used in waves

5 terms

Cover the right column and check you can say what each one means.

v, f, λ

Wave speed (m s⁻¹), frequency (Hz), wavelength (m) — related by v = fλ.

F

Focal length — the distance from a lens or mirror to its focal point, where parallel rays converge (or appear to diverge from).

Magnification

Image height ÷ object height — greater than 1 means enlarged, less than 1 means diminished; the sign shows upright (+) or inverted (−).

n, n₁, n₂

Refractive index — how much a medium slows light, relative to a vacuum; n₁ is the medium light leaves, n₂ the medium it enters.

Critical angle

The angle of incidence (in the denser medium) at which the refracted ray grazes along the boundary at 90° — beyond it, total internal reflection occurs.

Before writing anything

• Identify which recurring topic this part is: lenses/mirrors, refraction/TIR, or waves/interference/Doppler — each has its own checklist below.

Practice for this standard covers the whole topic — flashcards and quiz.