An object is kept at 60 cm in front of a convex lens. Its real image is formed at 20 cm from the lens . Find the focal length and power of the lens.

Explanation

To solve the problem, we will use the lens formula and the definition of power of a lens. Here’s the step-by-step solution:

### Step 1: Identify the given values
- Object distance (u) = -60 cm (negative because the object is on the left side of the lens)
- Image distance (v) = +20 cm (positive because the real image is formed on the right side of the lens)

### Step 2: Use the lens formula
The lens formula is given by:
...