Question

Object distance=20cm,image is formed at same distance. What is focal length?

Answer 1

Answer:

Explanation:

The primary measurement of a lens is its focal length. The focal length of a lens, expressed in millimeters, is the distance from the lens's optical center (or nodal point) to the image plane in the camera (often illustrated by a "Φ" on the top plate of a camera body) when the lens is focused at infinity.