16: 16 A source of sound S emitting waves of frequency 100 Hz and an observed O are - Physics - Magnetism And Matter

Question

16:

16 A source of sound S emitting waves of frequency 100 Hz and an
observed O are located at some distance from each other The source
is moving with a speed of 19 4 ms-1 at an angle of
60o with the source observed lines as shown in the
figure The observer is at rest The apparent frequency observed by
the observer (velocity of sound in air 330 ms-1), is

(1) 106 Hz (2) 97 Hz
(3) 100 Hz (4) 103 Hz

Anshu Agrawal · Accepted Answer

Dear student,

The apparent frequency heard $straight f subscript straight o space equals space straight f subscript straight s open square brackets fraction numerator straight V over denominator straight v minus straight v subscript straight s space cos space 60 to the power of straight o end fraction close square brackets space equals space 100 space open square brackets fraction numerator 330 over denominator 330 minus 19 4 space straight x begin display style 1 half end style end fraction close square brackets equals space 100 space open square brackets fraction numerator 330 over denominator 300 minus 9 7 end fraction close square brackets space equals space 100 open square brackets fraction numerator 330 over denominator 320 3 end fraction close square brackets equals space 103 02 space Hz$ Regards