Total internal reflection is possible when light rays travel

n_a, n_b and n_c are refractive indices of three media A, B, C respectively for a particular wavelength such that n_a> n_b> n_C . Total internal reflection is possible when light travels from

Total internal reflection takes place when the light ray travels from....

Total internal reflection takes place when the light ray travels from....

Total internal reflection of light is possible when light enters from