My book states it as $(\sin i)/(\sin r)=n$. However, University Physics has a different say. It says, $n_{a} \sin a =n_{b} \sin b$. Which of the following is correct?


The second one is more general.

In general, Snell's law can be stated as:


Where $n_1$ is the index of refraction of the medium of the incident ray, $n_2$ the index of refraction of the medium of the refracted ray, and $\theta_1$ and $\theta_2$ are the angles of the incident and refracted rays, respectively (with respect to the normal plane of refraction).

The first equation you have is a particular case where $n_1=1$, which is approximately the index of refraction of the air (many problems you'll encounter assume the incident ray comes from a medium of air)


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.