Question

(a) When we put our ear to a railway line, we can hear the sound of an approaching train even when the train is far off but its sound cannot be heard through the air. Why?
(b) How could you convince a small child that when you speak, it is not necessary for air to travel from you mouth to the ear of listener?

Answer 1

(a) Sound travels about 15 times faster in iron or steel than in air. We can hear the sound of an approaching train by putting our ear to the railway line made of iron or steel even when the train is far away because the sound produced by the motion of train’s wheels over the railway line is carried away quickly by the steel rails than in air.

(b) There is no actual movement of air from the sound-producing body to our ear. The air layers only vibrate back and forth and transfer the sound energy from one layer to the next layer and fall on our ears; the eardrums vibrate accordingly and reproduce the sound.