A teaching story
Teaching Guidance for 11-14
Different speeds of sound and light
You probably have a story like this one:
It's a Saturday afternoon and Anita, a keen football fan, is revising for her exams. She has the radio on quietly in the background to follow the progress of the match. In the last seconds of the match, the home team scores. Anita jumps up to the window, throws it open and puts her head outside to see if she can hear the roar of the crowd from the ground.
She is just about to close the window when there it is: the roar arrives from the football ground!
The football ground is about 3 km away. Sound travels at about 300 metres/second, giving about 10 second for the sound to travel from the ground to the house.
The radio wave signal to Anita's radio set travels at the speed of light, arriving 'instantaneously' while the sound takes rather longer to get there.