Describe an experiment, including a graphical analysis of the results to determine the focal length of a concave mirror using the No-Parallax method.

Describe an experiment, including a graphical analysis of the results to determine the focal length of a concave mirror using the No-Parallax method.

Or

You are provided with the following pieces of apparatus.

A screen with cross-wire, lamp, a concave mirror, and meter rule.

Describe an experiment to determine the focal length of concave using the above apparatus.

Solution

An object pin P1 is placed at a distance u in front of a mounted concave mirror so that its tip lies along the axis of the mirror.

A search pin P2 placed between the mirror and pin P1. P2  is adjusted until its image coincides with pin P1 by no-parallax.

The distance v of pin p2 from the mirror is measured.

The procedure is repeated for several values of u and the results are tabulated including values of uv, and u+v.

A graph of uv against u+v is plotted and the slope s of the graph is equal to the focal length f of the mirror.