According to the second law of refraction, for a definite pair of media and a particular colour of light —

• a$\sin\theta \times \sin\theta' = n$
• b$\sin\theta + \sin\theta' = n$
• c$\frac{\sin\theta}{\sin\theta'} = n$ (constant)
• d$\sin\theta - \sin\theta' = n$