Question

When the source of a wave is moving relative to an observer of the wave, which of the following is true?
A. observers ahead of the wave observe an apparent increase in wave frequency
B. observers both ahead of and behind the wave notice an increase in frequency
C. observers in all directions notice a decrease in wave frequency
D. observers behind the wave observe lower wavelengths and higher frequency

Answer 1

A.Because when the source is moving towards you it takes lesser time to travel with each wave.so time period decreases.Therefore,frequency increases.this is doppler effect

Answer 2

Oh alrite thank you cibychak ;)

Answer 3

:)