A slab of glass, of thickness 6 cm and refractive index `mu`=1.5 is placed in front of a concave mirror as shown in the figure. If the radius of curvature of the mirror is 40 cm and the reflected image coincides with the object, then the distance of the object from the mirror is

Answer

42 cm

Explanation

Shift due to glass slab =`6(1- (1)/(3//2))= 6 xx (1)/(3) = 2 cm`
t = thickness of glass slab, `mu = 3//2`
Reflected final image concides with the object when the effective distance of the object in equal to radius of curvature of mirror `u = 40 + 2 = 42 cm`.