Question

a person standing at a point 12m from a wall that produces an echo will not hear it.give reason

Answer 1

we know that to form an echo , the dist. to the reflector must be minimum at 7m , accordingly 14m dist. should be there for an distinct echo , as according to the question the dist. is 12m , it's oviously that the echo can't be heard by the boy , n the echo must form behind the boy

Answer 2

Answer: To hear an echo,the original sound and the reflected sound should be separated by a time interval of at least one tenth of a second. If two sounds occur within one-tenth of a second, you will not hear them as separate sounds. As a human ear cannot distinguish sounds if they are not separated by one-tenth of a second.