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 entering a substance - Leaving Cert Physics - Question 3 - 2005

The graph should plot sin(i) on the x-axis and sin(r) on the y-axis. To create the points, first calculate sin(i) and sin(r) using the recorded values. The axes must be clearly labeled. Make sure to plot at least five points accurately to show a straight-line correlation between the angles. When a straight line is drawn through the points, this indicates that sin(i) is proportional to sin(r), hence verifying Snell's law. Conclude with a statement that emphasizes this relationship and a correlation coefficient indicating the precision of the data.

To determine the refractive index (n), use Snell's law, which states that $n = \frac{\sin(i)}{\sin(r)}$ Select two corresponding values of sin(i) and sin(r) from the graph to calculate n. Use the correct method for slope, as the slope of the line represents the refractive index in this context. An example calculation using points from the graph: if sin(i) = 0.5 and sin(r) = 0.33, then the refractive index n can be calculated as follows: $n = \frac{0.5}{0.33} \approx 1.51$. However, referring to the given marking scheme, if the average is calculated correctly, the acceptable range for n could be from 1.44 to 1.50.

Smaller angles of incidence can lead to greater percentage errors in measurements due to increased susceptibility to minor inaccuracies in ray alignment and protractor reading. This results in larger relative errors when calculating sin values. As a consequence, the values measured become less reliable, and the relationship described by Snell's law could suffer from increased variability, hence reducing the accuracy of the experiment.