Focal lengths ii if you were handed an unmarked convex lens (no optical track) and asked to estimate its focal length quickly, how would you do it? explain.

Explanation:

To estimate the focal length of a convex lens follow the following steps.

1. take a convex lens.

2. Stand near a window which is just opposite to a wall.

3. Look at a tree which is far away from the window by the convex lens.

4. focus the image of the tree on the wall which is opposite to the window.

5. You wll observe that by changing the position of convex lens a sharp and inverted and small image is seen on the wall.

5. Now measure the distance between the lens and the wall.

7. This distance is the rough focal length of the convex lens.