To determine the refractive index of a glass slab using a travelling microscope | Cbse Class 12th physics practical

Objective

To determine the refractive index of glass by using travelling microscope.

Apparatus required

A travelling microscope with vernier scale, a glass slab, white paper, a pen and lycopodium powder.

Formula Used

Diagram

Observations

1. Least count of main scale of microscope = 0.5 mm.

2. Number of division on vernier scale=50

Calculation

Result

The refractive index of the glass slab by using travelling microscope = 1.48

PRECAUTIONS

• Microscope once focussed on the cross-mark, the focussing should not be disturbed throughout the experiment. Only rack and pinion screw should be used to raise the microscope upward.
• Only a thin layer of lycopodium powder should be spread on the top of the slab.
• The microscope tube should be vertical.
• Microscope should not be shaky.
• Eyepiece should be adjusted so that cross-wires are distinctly seen.
• As far as possible, the rack and pinion screw should be moved in one direction only to avoid backlash error.

SOURCES OF ERROR

• The scale used in the microscope might be caliberation property.
• Microscope tube may not be exactly vertical.
• The lycopodium powder layer on the glass slab might be thick.