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A car approaching a crossing C at a spe...

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 ?

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Verified by Experts

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`
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