# Thickness of the slab in Refraction of Light At Plane Surfaces – Class 10 Science Experiment

## Activity Name: Thickness of the slab in Refraction of Light At Plane Surfaces

### Activity Description:

In this experiment, we will measure the thickness of a glass slab using the concept of refraction of light. By observing the displacement of pins viewed through the slab, we will calculate the vertical shift and then use it to determine the refractive index of the glass.

### Required Items:

1. Glass slab
2. White chart
3. Pins
4. Ruler or measuring tape

### Step by Step Procedure:

1. Take a white chart and fix it on a table.
2. Place the glass slab in the middle of the chart and draw its boundary. Label the vertices of the rectangle formed as A, B, C, and D.
3. Draw a perpendicular to the longer line AB of the rectangle at any point on it.
4. Remove the slab and observe the lines you drew. They should form a rectangle.
5. Place the glass slab again within the rectangle ABCD.
6. Take a pin and position it at point P along the perpendicular line, with its length parallel to AB and at a distance of 15 cm from the slab.
7. Now, take another pin and look at the first pin from the opposite side of the slab. Try to position the second pin so that it forms a straight line with the first pin.
8. Remove the slab and observe the positions of the two pins.
9. Draw a perpendicular line from the second pin to the line on which the first pin was placed. Label the intersection point as Q.
10. Measure the distance between points P and Q. This distance is the vertical shift.

### Experiment Observations:

• The positions of the two pins appear to be in the same line when viewed through the glass slab.
• The distance between points P and Q represents the vertical shift.

### Precautions:

1. Ensure the glass slab is clean and free from any dirt or smudges that could affect the observations.
2. Handle the glass slab and pins with care to avoid any breakage or injuries.
3. Use a ruler or measuring tape for accurate measurements.

### Lesson Learnt from Experiment:

By observing the displacement of pins through a glass slab and measuring the vertical shift, we can determine the refractive index of the glass using the formula: Refractive Index (R.I) = Thickness of the slab / (Thickness of slab – Vertical shift). This experiment demonstrates the principles of refraction of light and how it can be used to calculate the refractive index of a transparent material.