Refraction

i + e = A + $\delta$  

Angle of deviation is the angle which the emergent ray makes in the direction of incident ray.

Angle if incidence i - With the increase in angle of incidence the angle of deviation first decreases to a minimum value of deviation after which it increases.

Material of the prism.

Colour or wavelength of light used Violet deviates more than red.

Angle of prism.

the refracted ray becomes parallel to base. i=e. So 2 i = A + $\delta$  

Find the angle of minimum deviation in a equilateral glass prism if i=48

 $\delta=2i-\ A\ =\ 2\times48-60=36\degree$  

Remember these above values for equilateral glass prism.