A siren of frequency n approaches a stationary observer and then receedes from the observer. If the velocity of source (V) lt ltthe velocity of sound (C ), the apparent change in frequency is

A siren of frequency n approaches a stationary observer and then recee

1.	A siren of frequency n approaches a stationary observer and then receedes from the observer. If the velocity of source (V) lt ltthe velocity of sound (C ), the apparent change in frequency is
Answer» `2nV//C` `2nC//V` `n//V` `2VC//n` Solution :`n.=n((V)/(V-V_(S)))=n((C )/(C-V))` `n..=n((C )/(C+V))` `Deltan..=n.-n..=NC[(1)/(C-V)-(1)/(C+V)]` `=nC[(2V)/(C^(2)-V^(2))]` `V^(2)`can be NEGLECTED as `V lt lt C :. Deltan.=(2nV)/(C )`