Hi everyone! Greetings from Komodo Craft. Today, we’re going to attempt a very interesting physics experiment: determining the refractive index of different liquids with a hollow prism. This is an excellent school science project or home science activity for children who’d enjoy seeing physics in action.

For this experiment, we shall use Snell’s Law to find the refractive index of various liquids. Don’t worry—we shall guide you through it step by step so that you are able to do it at home or for your school fair.

Even you can buy our kit from amazon .

Materials Needed

Before you start off, make sure you have the following materials:

1. Hollow prism (triangular prism which can be filled with liquid)

2. Liquids such as water, refined oil, and vegetable oil

3. Ruler and protractor for accurate measurements

4. Pencil or marker

5. Source of light (for a clear incident ray)

6. Clips or stand to hold the prism

Theory behind the Experiment

The experiment is based on Snell’s Law, which explains the refraction of light when it moves from one medium to another. The refractive index (n) of a medium indicates how much the light bends compared to air.

Snell’s Law equation:

n1sin (i) = n2 sin(r)

Where:

n1 = refractive index of medium 1 (air = 1)

n2 = refractive index of medium 2 (the liquid)

i = angle of incidence of light

r = angle of refraction within the liquid

Why this is interesting

Light is refracted at various angles in various liquids.

If you measure the angles accurately, you can calculate the refractive index of every liquid.

In this experiment, you come to understand the everyday application of physics.

Image Placeholder: Diagram of bending light inside a hollow prism filled with liquid

Step-by-Step Procedure

Carefully go through the steps to get accurate results:

1. Prepare Your Model Base, Graph Board and other equipment .

Attach them securely so that it won’t move.

2. Locate and Trace the Hollow Prism
Place the hollow prism on the sheet of paper.

Trace the shape and label the corners as A, B, and C.

3.Draw an incident ray at any angle to the normal.

Draw a normal line perpendicular to the front and back faces of the prism. 

4. Fill the Prism with Liquid
Carefully pour the liquid into the prism.

Don’t let air bubbles get in there—these will taint your readings.

5. Mark the Emergent Ray
Look through the prism and mark emergent ray along with the normal.

This is the emergent ray.

6. Draw and Measure Angles
Remove the prism and label the incident and emergent ray paths on a drawing.

Measure incidence (i) and refraction (r) angles using a protractor.

7. Do for Other Liquids
Try with refined oil, kerosine oil, or any other clear liquid.

Keep the prism in the same position to ensure consistency.

Working Out the Refractive Index

After you have measured the angles:

n of that liquid = sin (i) / sin (r)
i= angle of incidence

r = angle of refraction in the liquid

Tip: Take multiple readings for all of the liquids and calculate the mean for accurate results.

You can see the Sample Observation Table from the following pdf to see how your results look like –

PDF LINK

Precautions

For optimal results, follow these tips:

Employ a moderate incidence angle (30°–60°).

Mark the rays accurately to avoid errors.

Construct the normals cleanly with a ruler and protractor.

Do not measure angles by parallax.

Ensure the prism is upright and there is no leakage.

Repetition of the experiment for greater accuracy.

Conclusion

This hollow prism experiment is an excellent way to experiment with Snell’s Law and learn about the refraction of light in different liquids. Determining the refractive index provides first-hand experience of light refraction through the application of real-world physics concepts.

This activity is perfect for:

School science fairs

Physics experiments

Homework experiments

Try more liquids and even observe how temperature affects the refractive index. It is a highly fun and educational project that opens your eyes to learning more about light and optics.