I've just finished some past exam papers and when marking them using the mark scheme something confused me a little
One question said when a fire engine moves away from an observer, the pitch of the siren decreased, why and I chose the wavelength of the sound wave decreases
The mark scheme said the answer was the distance traveled by each wave front increases
I learned from my mistake and moved on. Today I've done another paper and a question says explain how the movement of the ambulance causes the frequency of the sound the man hears to change. Remembering my mistakes I talked about as the ambulance moves closer the distance traveled by each wavefront, decreases so there are more waves per second so f increases and the opposite for moving away, but the mark scheme said "higher frequency, wavelengths shorter as ambulance moves closer" Am I actually correct in what I'm saying or has the mark scheme got a case of double standards. Thanks in advance.