Guided lesson

The Wave Equation

3.53.63.7

3 guided lessons · 27 checks · 3. Waves → Waves & The Electromagnetic Spectrum

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Lesson 1 of 3

The wave speed equation

Every wave, from a stadium ripple to a gamma ray, obeys one speed law: wave speed equals frequency multiplied by wavelength. In symbols, v = f x lambda, with v in metres per second, f in hertz and lambda in metres. A formula triangle makes rearranging it a covering exercise rather than algebra.

What you know already

You can already define wave speed, frequency and wavelength, and you know every wave obeys the same rhythm. One small equation now ties those three together, and a second links frequency with the time period. With them you can work wave questions for ripples, sound and light alike, which is exactly what this lesson trains.

Key points of understanding

All waves obey the wave speed equation v = f x lambda.
v is the wave speed in metres per second.
f is the frequency in hertz and lambda the wavelength in metres.
A formula triangle covers the quantity you want to find and reads off the arrangement of the other two.

Wave speed triangle (2), IGCSE & GCSE Physics revision notes — A formula triangle can be used to help rearrange the wave speed equation

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1.The wave speed equation

3.5

Key points

All waves obey the wave speed equation v = f x lambda.
v is the wave speed in metres per second.
f is the frequency in hertz and lambda the wavelength in metres.

Guided content from the SME authoring corpus — note rn_hkV9ncw6zTQqrbN5, pinned at dad406f1ecd8 · promoted SyllabAI/syllabai-resources b3caaaa90c5e

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2.Frequency & time period

3.6

Frequency and time period are two views of one rhythm, and the equation f = 1 / T converts between them. Divide one second by the period and you have the count of waves per second; turn the frequency upside down and you have the seconds per wave. The worked example puts the sums to work on light itself.

3.Using the relationships in different contexts

3.7

The two relationships are not tied to any one wave type: sound in air, ripples on water and light in space all answer to v = f x lambda and f = 1 / T. Exam questions simply dress the same algebra in different contexts, so the skill is spotting which quantity each sentence hands you and converting units first.