Key learning points

1. Frequency of a wave can be measured indirectly from its speed and wavelength.
2. Wavelength of a wave can be measured by using a freeze frame of a wave moving along the length of a ruler.
3. It is more accurate to measure the length of, e.g. ten waves and dividing by ten, than measuring one wavelength.
4. Speed of a wave can be measured by recording the wave moving along a ruler with a timer in the frame.
5. Accurate distance and time are measured by freezing the film, played back in slow motion, to track one wave crest.

Keywords

• Ripple tank - A vibrating beam in a ripple tank creates water waves in a clear bottomed container that makes the waves easier to observe.

• Slow motion - A film played back in slow motion shows everything happening slowly, including the speed of a timer shown in the film.

• Wave equation - The wave equation is: wave speed = frequency × wavelength, v = f × λ.

• Uncertainty - The uncertainty in a measurement can be expressed as the range of values within which the true value must lie.

• Significant figures - The number of significant figures of a measurement depends on how accurately the measurement is made.

Common misconception