Question

An observer moves towards a stationary source of sound with a velocity one-fifth of the velocity of sound. The percentage increase in the apparent frequency heard by the observer will be ______.

Options

• 20%

• 0.5%

• 10%

• 5%

Answer 1

An observer moves towards a stationary source of sound with a velocity one-fifth of the velocity of sound. The percentage increase in the apparent frequency heard by the observer will be 20%.

Explanation:

`"V"_0 = "V"/5`

`"v"_"a" = "v"_0 ("v" + "v"_0)/"v" = "v"("v" + "v"/5)/"v" = "v"_0 6/5`

`("v"_"a" - "v"_0)/"v"_0 xx 100 = ((6/5 - 1)"v"_0)/"v"_0 xx 100`

`= 1/5 xx 100` = 20 %