A stationary sound source emits frequency f in still air. An observer moves directly towards the source with speed uₒ. Which statement about the wavelength in the air and the observed frequency is correct?

Options

• Option A

  The wavelength in the air decreases because the observer moves towards the source.

• Option B

  The wavelength in the air increases because the observer moves towards the source.

• Option C

  The wavelength in the air remains v/f, but the observer encounters wavefronts at a greater rate.

• Option D

  Both wavelength and frequency of the wave in the medium increase.