The condition for minimum deviation through a prism is that angle of incidence (i) is equal to angle of emergence ( e).In that case, the refracted ray `EF` becomes parallel to the base `bC` of the prism.
If `D_m` is the angle of minimum deviation, then the prism formula is
`mu =(sin(A + D_m)//2)/(sin A//2)`
Here, `mu`is refraction index of the material of the prism.
