Question
Question: A point object O is placed at a distance of 20 cm from a convex lens of focal length 10 cm as shown ...
A point object O is placed at a distance of 20 cm from a convex lens of focal length 10 cm as shown in figure. At what distance x from the lens should a concave mirror of focal length 60 cm. be placed so that final image coincides with the object –
A
10 cm
B
40 cm
C
20 cm
D
Final image can never coincide with the object in the given conditions
Answer
20 cm
Explanation
Solution
Object is placed at distance of 2f from the lens i.e. the image formed by the lens will be at a distance of 2f or 20 cm from the lens. So if the concave mirror is placed in this position the first image will be formed at its pole & it will reflect all rays symmetrically to other side.
