In an experiment to determine the refractive index of glass, light was passed through a glass block and the angles of incidence $i$ and refraction $r$ were measured for different values of $i$ - Leaving Cert Physics - Question 2 - 2020

Using a smaller angle of incidence can result in a larger percentage error in measuring the angle of refraction. This tendency occurs because small angles are harder to measure accurately due to the limitations of the protractor's scale, leading to greater uncertainty in the results.

To verify Snell's law, we can plot a graph of rac{ ext{sin}~i}{ ext{sin}~r} against the angle of incidence $i$. For this, first, we calculate $ext{sin}~i$ and $ext{sin}~r$ for the provided values of $i$ and corresponding $r$. Then we can label the axes appropriately and include a linear fit through the data points.

The graph verifies Snell's law if it shows a linear relationship that passes through the origin. According to Snell's law, the ratio rac{ ext{sin}~i}{ ext{sin}~r} should be constant for all points, indicating that as angle $i$ increases, angle $r$ also increases linearly. This means the points should lie on a straight line, verifying the law.

To calculate the refractive index $n$ of the glass, we can use the slope $m$ of the line in the graph. The refractive index can be determined using the formula: n = rac{ ext{sin}~i}{ ext{sin}~r} From the graph, if we take two points on the line, we can substitute these into the formula to find $n$. For example, if $m = 1.50$, then the refractive index of the glass is $n = 1.50$.