Question

Calculate the critical angle for a glass air interface, if a ray of light incident in air on the surface is deviated through `15^@`, when its angle of incidence is `40^@`.

Answer 1

Here, `C = ?, i = 40^(@)`,
deviation, `delta = 15^(@)`
As ray devitates towards normal., therefore,
`r = i - delta = 40^(@) - 15^(@) = 25^(@)`.
As `mu = (sin i)/(sin r) = (1)/(sin C)`
`:. sin C = (sin r)/(sin i) = (sin 25^(@))/(sin 40^(@)) = (0.4226)/(0.6428) = 0.6574`
`C = sin^(-1)(0.6574) = 41.1^(@)`