describe an activity to determine the principal focus and rough focal length of a concave mirror

Hi Nishkala!

The following activity can be used to determine the principal focus and approximate focal length of a concave mirror.

(1)  Place the mirror vertically on a table.

(2)  Place an object (a pencil) in front of the mirror and move it towards and away from the mirror.

(3)  Find the approximate spot where the reflection of the object changes from upright to upside down. This point is the focus of the mirror. Measure the distance between this point and the mirror. This length is the focal length of the mirror.

Cheers!!