On a windless day a boy standing in front of a high cliff shouts once and listens for the reflected sound.
(a) If the speed of sound in air is 340m/s, calculate the minimum distance that must separate the boy from the cliff for him to hear a distinct echo.
(b) The actual horizontal distance between the boy and the cliff is 255m. Determine the time gap between the shout and the echo that he will hear.
(c) Would the boy hear a distinct echo if he were only 40m from the cliff? Give a brief reason for your answer.