Definition (Law of Refraction).
- The refracted ray lies in the plane of incidence
- The angle of incidence $\theta_1$ and angle of refraction $\theta_2$ are related by Snell’s Law
- Linear (small-angle) approximation: $n_1 \theta_{1} \approx n_{2} \theta_{2} \implies \theta_{2} \approx \left(\frac{n_{1}}{n_{2}}\right)\theta_{1}$
- A third angle, the angle of deviation, represents
the difference between the angles of incidence and refraction
[Course handout, Introduction to Ophthalmic Optics, p. 15]- Since it lies between $\theta_{1}$ and $\theta_{2}$, $\theta_{d} \coloneqq \theta_{1} - \theta_{2}$
Sources
- Course handout, Introduction to Ophthalmic Optics