Question

Find the co-ordinates of image of the point object ‘o’ formed after reflection from concave mirror as shown in fig. Assuming prism to be thin and small in size of prism angle 2º Refractive index of prism material is (3/2). 

Answer 1

Consider image formation through prism. All incident rays will be deviated by 

δ = (μ-1)A = [(3/2)-1]2º= 1º = (π/180) rad 

Now as prism is thin so object and image will be in same plan as shown in fig. 

It is clear d/5 = tan δ = δ                     (∵ δ is very small) 

or d = (π/36) cm 

Now this image will act as an object for concave mirror 

u = -25 cm, f = -30 cm 

v = uf/(u-f) = 150 cm 

Also, m = -v/u = +6 

∴ Distance of image from principal axis = (π/36)6 = π/6 cm 

Hence, co-ordinates of image formed after reflection from concave mirror are 

(175cm, π/6 cm)