Question

To find the focal length of convex lens experiment​

Answer 1

Answer:

For a thin lens in air, the focal length is the distance from the center of the lens to the principal foci (or focal points) of the lens. For a converging lens (for example a convex lens), the focal length is positive and is the distance at which a beam of collimated light will be focused to a single spot.

Answer 2

To Find the Focal Length of a Convex Lens by Plotting Graphs Between U and V or Between

To Find the Focal Length of a Convex Lens by Plotting Graphs Between U and V or Between 1/u and 1/v

Aim

To find, the focal length of a convex lens by plotting graphs between u and v or between 1/u and 1/v.

Apparatus

An optical bench with three uprights (central upright fixed, two outer uprights with lateral movement), a convex lens with lens holder, two optical needles, (one thin, one thick) a knitting needle and a half metre scale.

Theory

The relation between u, v and f for a convex lens is

to-find-the-focal-length-of-a-convex-lens-by-plotting-graphs-between-u-and-v-or-between-1u-and-1v-1

where,

f = focal length of convex lens

u = distance of object needle from optical centre of the lens

v = distance of image needle from optical centre of the lens.

Note. According to sign-convention, u has negative value and v has positive value. Hence, f comes positive.

Ray diagram

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