A school student stands at the entrance of a long, straight tunnel and claps her hands once. She hears the first echo after 0.30s.
(a) Assuming the speed of sound in air to be 340m/s, calculate the distance from the student to the far end-wall of the tunnel.
(b) The clap has a dominant frequency of 680Hz. Find the wavelength of this sound in air.
(c) Suppose the tunnel is half-filled with water and the same clap travels through water to reach the far end-wall. Taking the speed of sound in water as 1500m/s and assuming the student is still at the entrance, calculate the time interval that would now elapse before the first echo is heard through water.
(d) Based on your calculations, explain why echoes are more commonly heard in air than in water for everyday sounds.