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Question
Answer briefly.
State the expression for apparent frequency when source of sound and listener are
- moving towards each other
- moving away from each other
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Solution
- Let, n0 = actual frequency of the source.
n = apparent frequency of the source.
v = velocity of sound in air.
vs = velocity of the source.
vL = velocity of the listener. - Apparent frequency heard by the listener is given by, n =`"n"_0 (("v" +- "v"_"L")/("v" bar+ "v"_"s"))`
Where upper signs (+ ve in numerator and -ve in denominator) indicate that the source and observer move towards each other. Lower signs (-ve in numerator and +ve in denominator) indicate that the source and listener move away from each other. - If source and listener are moving towards each other, then apparent frequency is given by,
n = `"n"_0(("v" + "v"_"L")/("v" - "v"_"s"))` i.e., apparent frequency increases. - If source and listener are moving away from each other, then apparent frequency is given by,
n = `"n"_0(("v" - "v"_"L")/("v" + "v"_"s"))` i.e., apparent frequency decreases.
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