A fire truck with its siren blowing passes you. What happens to the sound of its siren as the truck moves away from you?

A. the pitch gets higher
B. the pitch gets lower
C. the amplitude gets higher
D. the amplitude gets lower

Question

A fire truck with its siren blowing passes you. What happens to the sound of its siren as the truck moves away from you?

A. the pitch gets higher
B. the pitch gets lower
C. the amplitude gets higher
D. the amplitude gets lower

michele_laino · Answer

here the Doppler effect is involved

anonymous · Answer

ok! what does that mean? :/ pitch gets lower?

michele_laino · Answer

since the source of the sound is going away from me, then the received frequency from me, is less than the emitted frequency by the truck

anonymous · Answer

ohh so the solution should be amplitude is lower? choice D?

michele_laino · Answer

I think that the answer is
the pitch gets higher, since we have the subsequent relationship between wave length and frequency:
$$\Large  \lambda  = \frac{v}{\nu }$$
where  v is the speed of sound

anonymous · Answer

ohhh okay! makes sense :) 

thank you!!!

michele_laino · Answer

:)