Question

According to the Doppler effect, if a car with a blowing horn is moving toward you, the pitch you hear will

Answer 1

B. Increase

Explanation:

The closer together the crests, the higher the frequency (or pitch)

Answer 2

If a car with a blowing horn is moving toward you, the pitch sounds higher than the actual emitted frequency.

Explanation:

In figure,

V= speed of wave

U= speed of car

When car moving towards you, then

Car travels a distance in time T = VT

Wave travels a distance in time T = UT

From figure,

change in wavelength (λ') = VT - UT= T(V-U)

Now,

V = λ' f' (f' →frequency observed by you)

f' = V ÷ λ' =
`(V)/(T(V-U))`

We know that

`(1)/(T)` = f

Then,

f' =
`(Vf)/(V-U)`

f' =
`(f)/(1-(U)/(V) )`

Hence, we can say that

frequency increases as source moves toward you.