A person deep inside water cannot hear sound produced in air. Why?

Explanation

As speed of sound in water is roughly four times the speed of sound in air, therefore
`mu=(sini)/(sinr)=(v_(a))/(v_(w))=(1)/(4)=0.25`
For refraction, `r_(max)=90^(@)`
`:. (sini)_(max)=0.25`
`:. i_(max)=sin^(-1)(0.25)~~1.4^(@).` That is why most of sound produced in air and falling at `/_igt14^(@)` gets reflected in air only and person deep inside water cannot hear the sound.