(b) State one major difference between microwaves and radio waves.

(c) (i) Estimate the wavelength in metres of X-rays.

(c) Determine the frequency of the X-rays.

A student is sitting on the beach, observing a power boat moving at speed on the sea. The boat has a siren emitting a constant sound of frequency $420 \mathrm{Hz}$. The boat moves around in a circular path with a speed of $25 \mathrm{m}{\mathrm{s}}^{-1}$. The student notices that the pitch of the siren changes with a regular pattern.

(a) Explain why the pitch of the siren changes, as observed by the student.

A student is sitting on the beach, observing a power boat moving at speed on the sea. The boat has a siren emitting a constant sound of frequency $420 \mathrm{Hz}$. The boat moves around in a circular path with a speed of $25 \mathrm{m}{\mathrm{s}}^{-1}$. The student notices that the pitch of the siren changes with a regular pattern.

(b) Determine the maximum and minimum frequencies that the student will hear.(Speed of sound in air $\left.=330 \mathrm{m}{ \mathrm{s}}^{-1}.\right)$

A student is sitting on the beach, observing a power boat moving at speed on the sea. The boat has a siren emitting a constant sound of frequency $420 \mathrm{Hz}$. The boat moves around in a circular path with a speed of $25 \mathrm{m}{\mathrm{s}}^{-1}$. The student notices that the pitch of the siren changes with a regular pattern.

(c) At which point in the boat's motion will the student hear the most high-pitched note? (Speed of sound in air $\left.=330 \mathrm{m}{ \mathrm{s}}^{-1}.\right)$

This diagram shows some air particles as a sound wave passes.

(a) On a copy of the diagram, mark:

(i) A region of the wave that shows a compression-label it $\mathrm{C}$.

This diagram shows some air particles as a sound wave passes.

(b) Describe how the particle labelled P moves as the wave passes.

This diagram shows some air particles as a sound wave passes.

(c) The sound wave has a frequency of $240 \mathrm{Hz}$. Explain, in terms of the movement of an individual particle, what this means.