Two sound waves of wave length 0.8m and 0.81m produces 8 beats per second in air. The respective frequencies of the two waves are

Explanation

`nu=n_1lamda=n_2lamda_2`
`n_2-n_1=8`
`thereforen_2=n_1-8 `
`n_1xx0.8 =(n_1-8)xx0.8`
solving` n_1=648Hz` `n_2=640Hz`