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

Explanation

The situation is as shown in figure.

`cos theta =80/100 = 4/5`
`:.` Apparent frequency is
`f_("app") =(v/(v - v_s cos theta)) f = (330/(330 - 20 xx 4/5)) (500)`
` =525.5 Hz`