Spark image

Refraction wave fronts

The following diagram shows the refraction of a plane wave at a plane interface. The position of the refracted wave is formed using the idea of secondary wavelets.


One side of the wave moves from A to C (a distance vgt) in glass in the same time that the other side of the wavefront moves from B to D (a distance vat) in the same time in air. The wave front recombines at CD.

The angle of incidence in air is qa and the angle of refraction in glass is qg.

sin qa = vat/AD and sin qg = vgt/AD

Therefore sin qa/ sin qg = vat/vgt = va/vg = n and this is Snell's law of refraction.

schoolphysics plane wave refraction animation

To see an animation of the refraction of plane waves click on the animation link.


 

A VERSION IN WORD IS AVAILABLE ON THE SCHOOLPHYSICS USB
 
 
 
 
© Keith Gibbs