MYP Physics sample question: Wave speed, frequency and wavelength

A water wave on a pond has a frequency of 2.5 Hz and a wavelength of 0.40 m.

1. (a)Calculate the speed of the wave.[2]
   Show the mark scheme for (a)

   • • v = fλ (1)
   • • v = 2.5 × 0.40 = 1.0 m/s (1)
2. (b)The wave moves into shallower water, where its speed falls to 0.60 m/s. The frequency does not change. Calculate the new wavelength.[2]
   Show the mark scheme for (b)

   • • λ = v ÷ f (1)
   • • λ = 0.60 ÷ 2.5 = 0.24 m (1)
3. (c)State whether water waves are transverse or longitudinal and give one reason.[1]
   Show the mark scheme for (c)

   • • Transverse, because the water surface moves up and down at right angles to the direction the wave travels (1)

When a wave changes medium, frequency stays the same and speed and wavelength change together. Use that to decide which quantity to calculate.