For a transmission of wave from a dielectric medium of permittivity ε₁ into a dielectric medium of lower permittivity ε₂ and (ε₁ > ε₂) the critical angle of incidence θ_c (relative to the interface) is given by

A. $${\sin ^{ - 1}}\sqrt {\frac{{{\varepsilon _2}}}{{{\varepsilon _1}}}} $$

B. $${\cos ^{ - 1}}\sqrt {\frac{{{\varepsilon _2}}}{{{\varepsilon _1}}}} $$

C. $${\tan ^{ - 1}}\sqrt {\frac{{{\varepsilon _2}}}{{{\varepsilon _1}}}} $$

D. $${\sin ^{ - 1}}\sqrt {\frac{{{\varepsilon _1}}}{{{\varepsilon _2}}}} $$

Answer: Option A