Why does the refracted ray bend away from normal on travelling from denser to rarer medium?
1 Answer
When I consider the bending of the ray I always like to refer to Huygens Principle:
Explanation:
I like Huygens Principle because it is simple, easy to understand and gives you a practical way to explain the behaviour of light in interacting with matter.
Huygens tells us that light is a wave and if you consider the wavefronts (the crests, for example) of this wave he says that a new front is formed by the envelope of the spherical waves generated at each ppint of the previous front. It seems difficult but have a look:
The interesting thing is that the radius of each sperical wave will be dependent upon the VELOCITY of the wave (in that particular medium). So when the velocity of the wave changes, as when it passes from a medium to another having different density, also the radii of the sperical waves will change causing a change in the formation of the next front (and so producing the bending).
