In a beautiful valley, there was a village. When trains passed from the village, the whistle and the sound of train, mixed with the sound of waterfall, seemed to be very pleasant to everyone. Hence, children of that village used to play near the railway track. Once on a very light foggy day, a group of children found that a fish plate was missing from the track. As such, all the villagers were worried.
Prashant, one of the children, suddenly put his ear to the line and tried to know whether a train is coming or not. He knew a train is coming. He asked his friends to inform the railway cabin crew and he himself put off his red shirt and started running towards the train, waving his red shirt. The driver and cabin man got the alert signal in time and thus a major accident was averted.
Name the two physical phenomena of science used by Prashant.

Explanation

(a) Sound travels through a medium.
(b) Scattering of light