Question

How can you determine the focal length of a convex lens experimentally. Draw a rough diagram.

Answer 1

Concave lens:- focal length

Real lab procedure:

Keep the given convex lens of the known focal length $F1$ in the contact with the concave lens whose focal length is to be determine this forms the combination of the lenses.

It is placed between the illuminated wire gauge and the screen at fix distance away from the wire gauge.It is taken as Ucm.

The position of the screen is adjusted to get clear image on the wire gauge on the screen.

Measure the distance between the combination of the lenses and screen.It is taken as Vcm.

Calculate the focal length of the combination by using the given formula

$F=\frac{uv}{u+v}$cm

Repeat the experiment by placing the combination of lenses of different distances away from the wire gauge.