Explain with diagrams how refraction of incident light takes place from

a) rarer to denser medium

b) denser to rarer medium

c) normal to the surface separating the two media

Refraction of light take place when light travels between two medium. As the speed of light is different in different medium that is the major factor for refraction of light .

(a)

As you can see in this figure the light is travelling from less dense medium to more dense medium ,its path is deviated ,this is because of refraction taking place between these two medium.

Whenever the light travels from less dense medium to more dense medium it will bend towards the normal to the surface.

As you can see in the diagram incident ray bends towards the normal axis .

In this case always incident angle I > r (angle of refraction)

(b)

when the ray of light travels from more dense medium to less dense medium it move away from the normal axis. As you can see in the following figure

Consider the figure above when light ray passes through the interface of two medium it will deviated from its path . in this case always

Angle of incident I < r (angle of refraction)

(c) when the light ray incident normally to the interface of two medium then it travels in same path , no deviation will be there. Because the angle of incident will be 0.

You can see this in following figure –