A student carried out an experiment to verify Snell's Law and used her measurements to calculate the refractive index (n) of a material - Leaving Cert Physics - Question 2 - 2022

The angles measured should include:

• Angle of incidence (i) - the angle between the incident ray and the normal.
• Angle of refraction (r) - the angle between the refracted ray and the normal. Both angles should be clearly marked on the diagram.

The instrument used to measure these angles is a protractor.

The formula used to calculate the refractive index (n) is: $n = \frac{\sin i}{\sin r}$

To calculate the average refractive index:

1. Calculate n for each pair of angles using the formula:
   • For i = 30°, r = 19°:
     $n_1 = \frac{\sin(30)}{\sin(19)}$
   • For i = 40°, r = 25°:
     $n_2 = \frac{\sin(40)}{\sin(25)}$
   • For i = 50°, r = 31°:
     $n_3 = \frac{\sin(50)}{\sin(31)}$
   • For i = 60°, r = 35°:
     $n_4 = \frac{\sin(60)}{\sin(35)}$
2. Average these values: $n_{avg} = \frac{n_1 + n_2 + n_3 + n_4}{4}$

To verify Snell's Law, check whether the calculated values of n are consistent. If the values of n are similar (within a reasonable range), this indicates that Snell's law holds true for the material in question, thus confirming the law's validity as it relates to light's behavior at the interface between two media.

One precaution to improve accuracy is to ensure the use of a thinner pencil for the incident ray, which minimizes the thickness of the line, leading to better precision in angle measurement.