Energy transfer by progressive waves：練習問題

The intensity of a wave is doubled. By what factor does the amplitude of the wave change?

A point source emits sound waves uniformly in all directions. If the distance from the source is tripled, what happens to the intensity of the sound wave, assuming no energy is lost to the surroundings?

A source of sound emits power \( P \) uniformly in all directions. At a distance \( r \) from the source, the intensity is \( I \) and the amplitude of the pressure oscillation is \( A \). At what distance from the source would the amplitude of the pressure oscillation be \( 0.5 A \)?

Which of the following quantities is defined as the power transferred by a wave per unit area perpendicular to the direction of wave propagation?

A point source radiates energy uniformly in all directions. If the intensity of the wave is \( I \) at a distance \( r \) from the source, determine the new intensity, in terms of \( I \), when the distance is increased to \( 3r \).

A point source of sound emits waves uniformly in all directions. A microphone is placed at a distance of \( 2.0 \text{ m} \) from the source and measures the intensity of the sound waves as \( 4.5 \times 10^{-6} \text{ W m}^{-2} \).