Question

In an experiment to find focal length of a concave mirror, a graph is drawn between the magnitudes of (u) and (v). The graph looks like.

Answer 1

for a concave mirror

Let 1/image distance = x and 1/object distance = y. and 1/ focal length = k

(1/v + 1/u = 1/f)

We know 1/image distance + 1/object distance = [1/ focal length ]

Hence

x +y = k

y = - x + k and the graph is straight line and hence the slope of this straight line is -1.

Comparing it with the equation of y = mx + c m = -1 and c = k.