Question

In the given diagram, two transparent optical media are shown. The rarer medium is air, while the denser medium is water. Redraw the diagram by showing the paths of the rays after striking the surface of separation AD for the incident rays OA, OB, OC and OD, respectively. (Critical angle for the denser medium = 48°)

Answer 1

Critical angle for the denser medium = 48°

• OA: Falls along the normal (angle of incidence 0°), so it goes straight into air without bending.
• OB: Angle of incidence 42° is less than 48°, so it refracts into air, bending away from the normal (angle of refraction ≈ 64°).
• OC: Angle of incidence 48° equals the critical angle, so the angle of refraction is 90°. The ray grazes along the surface AD.
• OD: Angle of incidence 60° is greater than 48°, so it is totally internally reflected back into the water at 60°.