CATAGORY: Sound & Waves QUESTION: Light moves from flint glass into water at an angle of incidence of 28.7 degress; (a) What is the angle of refraction? (b) At what angle would light have to be incident to give an angle of refraction of 90.0 degrees?

## Back to Trinklein catalog.

Part A We will call the angle of incidence i and the angle of refraction r. Applying snells law (1) n(i)sin(i) = n(r)sin(r) Where n(i) and n(r) are index of refraction for mediums the incident (i) and refracted (r) rays are traveling in. n(i) = 1.58 (light flint glass) n(r) = 1.33 (water). Substituting the n's and i =28.7 degrees into equation (1) gives 1.58 sin(28.7) = 1.33 sin(r) solving for sin(r) sin(r) = 1.58 sin(28.7) / 1.33 so sin(r) = .570 *********************** * * * r = 34.8 (degrees) * * * *********************** Part B when r = 90 degrees sin(r) = 1.0 so snells law becomes (2) n(i)sin(i) = n(r) So sin(i) = n(r)/n(i) Substituting the n values gives sin(i) = 1.33/1.58 = .842 *********************** * * * i = 57.3 (degrees) * * * ***********************