June 2, 2011

3.19 calculating the refractive index

Describe an experiment to determine the refractive index of glass, using a glass block.

Using the formula for refractive index isn't too hard once you've tried it a few times...

taking the glass block from the worksheet in the previous post...
the angle of incidence is 40°
and the angle of refraction is 25°
so:
$n = \frac{\textup{sin}\, i}{\textup{sin}\, r}$

$n = \frac{\textup{sin}\, 40}{\textup{sin}\, 25}$

$n = \frac{0.6427...}{0.4226...}$

$n = 1.5209...$

$n \approx 1.52$

so the refractive index of a perspex block is roughly 1.52 (but remember there aren't any units)