The critical angle for a beam of light traveling between water and air is 49°.
(a) A beam strikes a water or air boundary and undergoes total internal reflection.Will the beam stay in the air or in the water?
(b) Explain what happens when a beam of light from the air strikes the surface of a calm lake at an angle of 50° from the normal
a) If the critical angle for total internal reflection is 49°, then any beam of light traveling between water and air at an angle greater than 49° will undergo total internal reflection and stay within the water. This means that the beam will not be able to pass through the boundary and will be reflected back into the water.
b) When a beam of light from the air strikes the surface of a calm lake at an angle of 50° from the normal, the angle of incidence is greater than the critical angle of 49°. This means that total internal reflection will occur and the beam of light will be reflected back into the air. The light will not be able to pass through the boundary and will stay within the air. This is why we often see reflections of the sky and surrounding objects on the surface of calm water bodies such as lakes.