CBSE Class 12 Physics Practical Section B Exp-7

Experiment – 7

Objective

To find the refractive index of liquid by using convex lens and plane mirror.

Apparatus required

A convex lens, a plane mirror, optical needle, water, an iron stand with base and meter scale.

Formula Used

The refractive index of a liquid by using a convex lens and plane mirror

R= focal length of convex lens.

F= focal length of compound lens formed by convex lens and plano-concave lens of water.

Diagram

1) Mean of fg = (17.5 + 17.4 )/2 =17.45 ≈17.5cm

2) Mean of F = (26+25.9)/2 = 26 cm

Precautions

1. Only a few drops of liquid should be taken so as not to thicken the layer.

2. The parallax should be removed tip to tip.

3. The liquid taken should be transparent.

Sources of Error

1. The liquid may not be quite transparent.

2. The parallax may not be fully removed.