Aim
To study the refraction of light through a triangular prism and observe how light bends as it passes through different media, illustrating the concept of light deviation and the change in direction at the interfaces of the prism. This experiment helps in understanding how the refractive index of the prism material affects the behavior of light passing through it.
Materials Required
- Triangular prism (made of glass or any transparent material)
- Laser pointer (to provide a focused light source)
- Protractor (to measure angles of incidence, refraction, and deviation)
- Paper (to trace and record the light path)
- Ruler (optional, for drawing straight lines)
Image Reference
Procedure
- Place the triangular prism on the paper and trace its outline carefully so that you can align the laser beam precisely.
- Shine a laser beam through one side of the prism, ensuring that the angle of incidence is measurable using the protractor.
- Observe and trace the path of the refracted ray inside the prism and the emergent ray exiting the other side.
- Measure the angle of incidence (the angle between the incoming light and the normal to the surface), the angle of refraction (the angle between the refracted ray and the normal), and the angle of deviation (the angle between the initial and final direction of the ray). Record these angles.
- Repeat the experiment for different angles of incidence and observe the variation in the angle of deviation.
Observation
The light ray bends twice—once when entering the prism (refraction) and once when exiting (second refraction). The angle of deviation depends on the angle of incidence and the refractive index of the prism material. The greater the angle of incidence, the greater the deviation.
Precautions
- Ensure that the laser beam is aligned accurately with the prism surfaces to avoid measurement errors.
- Use a sharp laser pointer for clear observation of the light path.
- Ensure that the protractor is aligned properly with the normal for accurate angle measurements.
- Perform the experiment in a dimly lit room for better visibility of the laser beam.
Conclusion
This experiment demonstrates the phenomenon of refraction and the bending of light as it passes through a triangular prism. It confirms that light changes direction at each interface due to the difference in the refractive index between the air and the prism material. The angle of deviation increases as the angle of incidence increases, and this relationship is governed by Snell's law.