A convex lens of focal length `20 cm` is placed co-axially with a convex mirror of radius of curvature `20 cm`. The two are kept `15 cm` apart from each other. A point object is placed `60 cm` in front of the convex lens. Find the position of the image formed by the combination.

Explanation

Here, `u=-60 cm,f=20cm`
From the lens formula, we have
`(1)/(v)-(1)/(u)=(1)/(f)`
`(1)/(v)=(1)/(f)+(1)/(u)rArr(1)/(v)=(1)/(120)+(1)/((-60))`

`rArr " " v = 60 cm`
The positive sign shows that the image is formed to the right of teh lens.
`(1)/(v)+(1)/(u)=(1)/(f)`
`u=-60 and f=20cm`
`(1)/(v)=(1)/(f)-(1)/(u)=(1)/(20)+(1)/(60)=(4)/(60)=(1)/(15)`
`rArr " " v = 15 cm`.