A convex lens and a convex mirror of radius of curvature `20 cm` are placed co-axially with the convex mirror placed at a distance of `30 cm` from the lens. For a point object at a distance of `25 cm` from the lens, the final image due to this combination coincides with the object itself. What is the focal length of convex lens ?

Explanation

To find the focal length of the convex lens in the given setup, we can follow these steps:

### Step 1: Understand the Setup
We have a convex lens and a convex mirror placed coaxially. The radius of curvature (R) of the convex mirror is given as 20 cm. The distance between the lens and the mirror is 30 cm, and there is a point object located 25 cm from the lens.

### Step 2: Determine the Focal Length of the Convex Mirror
The focal length (f) of a mirror is related to its radius of curvature (R) by the formula:
\[ f = \frac{R}{2} \]
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