Two transparent media A and B are separated by a plane boundary. The speed of light in those media are 1.5 × 10^{8 }m/s and 2.0 × 10^{8 }m/s, respectively. The critical angle for a ray of light for these two media is:

(1) tan^{-1}(0.500)

(2) tan^{-1}(0.750)

(3) sin^{-1}(0.500)

(4) sin^{-1}(0.750)