In an experiment to verify Snell’s law, a student measured the angle of incidence $i$ and the angle of refraction $r$ for a ray of light as it passes from air into glass - Leaving Cert Physics - Question 3 - 2022

The student determined the angle of refraction by measuring the angle between the refracted ray and the normal line to the surface at the point of incidence. This was done using a protractor to accurately measure the angles. The normal line was drawn at right angles to the surface at the point where the incident ray strikes the glass.

To verify Snell's law, plot a graph of $ext{sin}(r)$ on the y-axis against $ext{sin}(i)$ on the x-axis using the given data. The values are:

| $i$ (degrees) | $r$ (degrees) | $ext{sin}(i)$ | $ext{sin}(r)$ |
| 30 | 19 | 0.5 | 0.32 |
| 40 | 27 | 0.64 | 0.45 |
| 50 | 32 | 0.77 | 0.53 |
| 60 | 36 | 0.87 | 0.59 |
| 70 | 40 | 0.94 | 0.64 |
| 80 | 44 | 0.98 | 0.69 |

This graph should ideally yield a straight line indicating that Snell's law is verified.

Using the slope of the graph obtained from plotting $ext{sin}(r)$ against $ext{sin}(i)$, we can use the formula for the refractive index:

n = rac{ ext{sin}(i)}{ ext{sin}(r)}

For example, using the average slope from points on the graph, calculate the refractive index with a known pair of values. If we take $i = 30$ degrees and $r = 19$ degrees:

If the angle of incidence was zero degrees, it would be observed that there is no refraction of the ray. The ray would continue straight into the glass without changing its direction, essentially traveling along the normal line.