Aim : To find the focal length of a concave mirror.
Apparatus required.: Concave mirror, a sheet of paper and meter scale.
1) Hold a concave mirror perpendicular to the direction of sunlight.
2) Take a small paper and slowly move it in front of the mirror and find out the point where you get smallest and brightest spot.
3) This is the image of the sun.
4) The rays coming from sun parallel to the concave mirror are converging at a point.
5) This point is called focus or focal point (F) of the concave mirror.
6) Measure the distance of this spot from the pole of the mirror.
7) This distance is the focal length of the given concave mirror.