A car approaching a crossing `C` at a speed of `20 m//s` sounds a horn of frequency `500 H_(Z)` when `80 m` from the crossing . Speed of sound in air is `330 m//s` . What frequency is heard by an observer (at rest) `60m` from the crossing on the straight road which crosses car road at right angles ?

Explanation

The situation is as shown in figure

`costheta=(80)/(100)=(4)/(5)` `:.` Apparent frequency is
`n_(opp)=(v)/(v-v_(s)costheta)n=((330)/(330-20xx(4)/(5)))(500)=525.5Hz`