Calculate the refractive index of a slab if light incident at 40^ refracts at 26^ (assume incident medium is air).

The angle of incidence is $i = 40^\circ$.
The angle of refraction is $r = 26^\circ$.

Snell's Law states that the ratio of the sines of the angles of incidence and refraction is equal to the ratio of the refractive indices of the two media. Assuming the light is entering the slab from air (refractive index $n_1 \approx 1$), the refractive index of the slab material ($n_2$) can be found using the formula:

Since $n_1 = 1$ (for air), we have:

The refractive index of the slab material is approximately 1.47.