Question

The refractive index of air with respect to glass is expressed as ${}_g{\mu }_a$​ = $\frac{\sin i}{\sin r}$ if ∠ r = ${90}^{\circ }$​. What is the corresponding ∠i called?

• A. ∠i < ∠i_c
• B. ∠i > ∠i_c
• C. ∠i = ∠i_c
• D. None of these

Answer 1

The correct option is C

∠i = ∠i_c

The refractive index of air with respect to glass is expressed as ${}_g{\mu }_a$​​ = $\frac{\sin i}{\sin r}$

When ∠ r = ${90}^{\circ }$​ and sin ${90}^{\circ }$​​ = 1 (in the air).

∠i in the medium is called critical angle.