Fill in the blanks to complete the following sentences —

(a) Total internal reflection occurs only when a ray of light passes from a ………. medium to a ………. medium.

(b) Critical angle is the angle of ………. in denser medium for which the angle of ………. in rarer medium is ……….

State whether the following statement is true or false —

If the angle of incidence is greater than the critical angle, light is not refracted at all, when it falls on the surface from a denser medium to a rarer medium.

Name two factors which affect the critical angle for a given pair of media. State how do the factors affect it.

The refractive index of air with respect to glass is expressed as

${}_g{\mu }_a={\displaystyle \frac{\text{sin i}}{\text{sin r}}}$gμa = \dfrac {\text {sin i}}{\text {sin r}}

(a) Write down a similar expression for _aμ_g in terms of the angles i and r.

(b) If angle r = 90°, what is the corresponding angle i called?

(c) What is the physical significance of the angle i in part (b)?