Chapter 23, Problem 20Q

To determine

Where the position of the film be placed if a camera lens is to make a sharp image of an object far away.

Answer to Problem 20Q

Solution:

To make a sharp image of an object that is very far away, the film of a camera must be placed at the focal point of the lens. Objects that are very far away have light rays coming into the camera that are basically parallel and these rays will be bent and focused to create an image at the focal point of the lens, which is where the film should be in order to record a focused image.

Explanation of Solution

The camera is built to have a thin converging lens to focus the objects which are placed within the short range to the faraway objects.

The light rays from the, the different object, are coming to the camera as the parallel rays. Hence, the camera is receiving the parallel rays. After refraction at the both the convex surfaces of the lens the rays are converged at the focal point on the other side of the lens.

Hence, the film must be placed at the focal point of the camera, the other side of the focusing, which is the image of the distance object.

This is given by the following figure.