A convex lens of focal length 20 cm and a concave lens of focal length 15 cm are kept 30 cm apart with their principal axes coincident. When an object is placed 30 cm in front of the convex lens, calculate the position of the final image formed by the combination. Would this result change if the object were placed 30 cm in front of the concave lens ? Give reason.

Explanation

To solve the problem, we will follow these steps:

### Step 1: Determine the image position formed by the convex lens.

1. **Given Data:**
- Focal length of the convex lens (f₁) = +20 cm (positive because it is a convex lens)
- Object distance from the convex lens (u₁) = -30 cm (negative as per sign convention)

...