For total internal reflection to occur, I. light must be travelling from an optically more dense to an optically less dense medium. II. the angle of inciden...

For total internal reflection to occur,

I. light must be travelling from an optically more dense to an optically less dense medium.
II. the angle of incidence in the denser medium must be greater than its critical angle.
III. the angle of refraction in the less dense medium must be equal to 90 °. Which of the statements above is/are correct?