Refraction

• When a wave passes from one medium to another , it can be refracted and change direction - The direction change depends on : the angle at which the wave hits the boundary and the materials involved
• For light rays , the way in which a material affects refraction is called refractive index
• When light travels from a material with low refractive index to one with a higher refractive index , it bends towards the normal
• When light travels from a material with high refractive index to one with a low refractive index , it bends away from the normal
• Refraction is due to the difference in wave speed in the different media
• When a light wave enters (at an angle) a medium in which it travels slower : the first part of the light to enter the medium slows down - the rest of the wave continues at the higher speed - this causes the wave to change direction , towards the normal
• You need to be able to show what happens when light waves enter a medium in which it travels slower , using a wave front diagram