When an object is placed at the proper distance ot the left of a converging lens, the image is focused in a screen 30 cm to the right of lens. A dieverging lens is now placed 15 cm to the right of the converging lens and it is found that the screen must be moved `19.2cm` farther to the right to obtain a sharp image. Find the focal length of the diverging lens.

Explanation

To solve the problem, we need to find the focal length of the diverging lens based on the information provided. Let's break it down step by step.

### Step 1: Understand the Setup
- We have a converging lens (convex lens) that forms an image 30 cm to the right of it.
- A diverging lens (concave lens) is placed 15 cm to the right of the converging lens.
- When the diverging lens is added, the screen must be moved 19.2 cm farther to the right to obtain a sharp image.

### Step 2: Define Distances
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