Question
For a ray of light travelling from a denser, medium of refractive index n1 to a rarer medium of refractive index n2. Prove that n2 / n1= sin ic where ic is the critical angle of incidence for the media.
Solution
Given, a ray of light travelling from denser medium of refractive index n1 to a rarer medium of refractive index n2.
Snell's law is given by,
Now, critical angle is the angle of incidence in denser medium for which angle of refraction in rarer medium is 90o .
i.e., i = ic when r = 90o .
Thus, putting these values in snell's law , we have
i.e.,