A student carried out an experiment to verify Snell's law of refraction - Leaving Cert Physics - Question 3 - 2012

The student conducted the experiment as follows:

1. Refraction of Light: The student directed a laser beam towards the glass block at various angles of incidence.
2. Marking Points: The entry and exit points of the light ray were marked on the glass block with pins or dots.
3. Measuring Angles: Using a protractor, the angle of incidence i and the angle of refraction r were measured. This involved measuring the angle between the incoming ray and the normal to the surface at the point of incidence.
4. Repeating Steps: This process was repeated for different angles of incidence to gather a comprehensive set of data.

On the previously drawn diagram, indicate:

• Angle i: The angle formed between the incident ray and the normal at the surface of the glass block when the ray enters.
• Angle r: The angle formed between the refracted ray and the normal at the surface when the ray exits the glass.

Ensure that both angles are clearly marked and labeled on the diagram to illustrate their positions accurately.

The data in the completed table verifies Snell’s law of refraction as follows:

1. Sine Ratio: Snell's law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, or: $n = \frac{\sin i}{\sin r}$

2. Constant Value: By calculating the ratio of sin i to sin r for each angle pair in the table, one should observe that this ratio remains constant, confirming that Snell's law holds true in this experiment.

3. Example Calculation: For instance, for the first row: $n = \frac{0.423}{0.276} \approx 1.532$, which should approximate the refractive index of glass.