Physics (AS & A Level) · May / June 2026 · Paper 12 · Question 25

A source of sound of constant power P is situated in an open space. The intensity I of sound at distance r from this source is given by the equation shown. I = P / (4πr²) How does the amplitude a of the vibrating air molecules vary with the distance r from the source?

1. Aa ∝ 1/r
2. Ba ∝ 1/r²
3. Ca ∝ r
4. Da ∝ r²

As printed in the paper