A swimmer is at a depth of 4m below the calm surface of a lake of refractive index 1.33. Holding a narrow spotlight, he directs a beam of light towards the water–air interface.
(a) Calculate the critical angle for the water–air boundary.
(b) The beam strikes the interface with an angle of incidence 50∘ measured from the normal. State, with calculation, whether the light will emerge into air or be totally internally reflected back into water.
(c) If the angle of incidence is changed to 30∘, find the corresponding angle of refraction in air.