Verification of Snell’s law of refraction (and hence finding the refractive index of glass)

This experiment is on the Verification of Snell’s law of refraction (and hence finding the refractive index of glass).

Experiment: Verification of Snell’s law of refraction

Apparatus: light box, glass block, and protractor

Method: (refer to the diagram above)

• First, we have to place a glass block and mark its outline.
• Then we have to use the lightbox to shine a ray of light from it.
• Then, let’s mark the position of the light ray as it enters and leaves the block.
• Then, we have to remove the block.
• Then, we will draw in the normals and measure i and r, as shown in the diagram.

Now we have to plot a graph of sin i against sin r.

A straight line through the origin verifies Snell’s law of refraction, i.e. sin i is directly proportional to sin r.

The slope of the line is the refractive index.

Note: Larger angles will lead to a smaller percentage error.

This article is for science/physics students of the Leaving Certificate, and other boards like CBSE.