Work out total internal reflection instantly with clear inputs, formula shown and shareable results.
Snell's law, n1 sin(theta1) = n2 sin(theta2), decides the outcome at a boundary. Air into glass at 30 degrees refracts to 19.47 degrees, bending towards the normal. Going the other way, if the required sine exceeds one there is no solution and the light is totally internally reflected instead.
Snell's law
n1 sin(theta1) = n2 sin(theta2)
Total internal reflection
occurs when n1 sin(theta1) / n2 > 1
sin(theta2) = 1.0 x sin(30) / 1.5 = 0.3333, so the refracted ray is at 19.47 degrees.
Never. The refracted sine is always smaller than the incident one, so a solution always exists.