Question

When the source of a wave is moving relative to an observer of the wave, which of the following is true?

o observers ahead of the wave observe an apparent increase in wave frequency
observers both ahead of and behind the wave notice an increase in frequency
observers in all directions notice a decrease in wave frequency
observers behind the wave observe lower wavelengths and higher frequency

Answer 1

Observers ahead of the wave observe an apparent increase in wave frequency

Step-by-step explanation:

This is the Doppler Effect. The frequency of a wave increases when the source approaches the observer and decreases as the source recedes.

B, C, and D are wrong. Observers behind the source notice a decrease in frequency.