Two transparent media, turpentine oil and crown glass, have absolute refractive indices of 1.47 and 1.52 respectively.
(a) Explain, using suitable physical reasoning, why a ray of light bends towards the normal when it travels from turpentine oil into crown glass.
(b) Determine the relative refractive index of crown glass with respect to turpentine oil and hence decide whether light speeds up or slows down as it enters the glass.
(c) If a ray enters the glass from the oil at an angle of incidence of 30∘, predict qualitatively (without numerical calculation) whether the angle of refraction will be greater than, equal to, or less than 30∘. Justify your answer.