Question

A sound wave traveling in 20ºC air has a pressure amplitude of 0.5 Pa. What is the intensity of the wave?

Answer 1

`I=3.03×10^(-4)W/m^2.`

Intensity is defined as power over an area. It's given by

`I=P/A`

where
`I ->` intensity; `W/m^2`
`P->` power; `W`
`A ->` area; `m^2`

The intensity of a sound wave is given by the following eq'n:

`I=(Deltap)^2/(2rhov_w)`

where
`I ->` intensity; `W/m^2`
`Deltap ->` pressure variation/pressure amplitude `Pa or N/m^2`
`rho ->` density of material; `(kg)/m^3`
`v_w ->` speed of sound in medium; `m/s`

Given this equation, along with constants, you can substitute your values and solve.

The constant for the speed of sound in air at 20*C is 343`m/s`.
The density of air is 1.2041 `(kg)/m^3`.

`I=0.5^2/(2(1.2041)(343))=3.026588214271792*10^(-4)`
`3.03*10^(-4)W/m^2.`

I use my Physics for Scientists and Engineers (9th ed.) and my professor's notes to find equations and constants for most problems, including this one. Good luck!