Question

To find the focal length of a convex lens by plotting graphs between u and v readings

Answer 1

we know, lens maker formula,
1/v - 1/u = 1/f

where v is distance of image from the pole of lens, u is distance of object from the pole of lens and f is focal length of lens.

because, it is given that lens is convex lens
so, focal length be positive.

if we assume 1/v = y , 1/u = mx and 1/f = c

then, graph 1/v v/s 1/u is y = mx + c [ a straight line ] graph is shown in figure.

but when we want to plot graph v v/s u,
then its graph will be hyperbolic. graph is shown in 2nd figure.