Question

A source of sound is moving with constant velocity of 30 mis emitting a note of frequency 256 Hz. The ratio of frequencies observed by a stationary observer while the source is approaching him and after it crosses him is ______. (speed of sound in air = 330 m/s)

विकल्प

• 6 : 5

• 9 : 8

• 5 : 6

• 8 : 9

Answer 1

A source of sound is moving with constant velocity of 30 mis emitting a note of frequency 256 Hz. The ratio of frequencies observed by a stationary observer while the source is approaching him and after it crosses him is 6 : 5.

Explanation:

V_s = 30 m/s  n₀ = 256 Hz

`"n"_1 = "n"_0"V"/("V - V"_"s")`

`"n"_2 = "n"_0 "V"/("V + V"_s)`

`therefore "n"_1/"n"_2 = ("V + V"_"s")/("V - V"_"s") = 360/300 = 6/5`