Question

How do you find the focal length of lens experimentally

Answer 1

Answer:

1/v-1/u=1/f is the formula

Answer 2

Answer:

Aim : To determine the focal length of a convex lens.

Apparatus : Convex lens, meter scales, V-stand, screen, candle.

Procedure :

i) Place the convex lens on a ‘V’ stand. .

ii) Light a candle and take it far away from the lens along the principal axis.

iii) Adjust the screen on the other side of the lens to get a clear image on it.

iv) Measure the distance between the ‘V’ stand and the screen which gives a rough idea of focal length of the lens.

U-V Method : (Displacement method)

Now place the candle at a distance of 60 cm from the lens, such that the flame of the candle lies along the principal axis of the lens.

Adjust the screen t© get a clear image and measure the values of object distance (u) and image distance (v) and note them in a table.

Repeat the above step for various distances like 50 cm, 40 cm, 30 cm etc., note the corresponding (v) values.