A point source of light S is placed on the major optical axis of the concave mirror at a distance of 60 cm. At what distance from the concave mirror should a flat mirror be placed for the rays to converge again at the point S having been reflected from the concave mirror and then from the flat one? Will the position of the point where the rays meet change if they are first reflected from the flat mirror? The radius of the concave mirror is 80 cm.

Answer

C

Explanation

Using mirror formula,` (1/v+1/u=1/f)` for concave mirror first, we have
`(1/v-1/60=1/(-40)) ( :' F=R/2)`
or, `v=-120 cm`
First image `I_(I) at 120cm` from concave mirror will act as virtual object for p,ane mirror .Plane mirror will from real image of `(I_(1)` at S.

Ray diagram is shown in figure.
Distance between two mirror is 90 cm.