Consider that a ray of light is travelling from glass to water. the refractive index of water is 1.30 (i e n . , 1.30 w = ) and refractive index of glass is 1.70 (i e n . , 1.70 g = ). again, remind yourself that light is incident from glass to water. at the glass-water interface the light suffers total internal reflection (tir). find the condition for total internal reflection

Explanation:

Total internal reflection can happen when light goes from a medium with higher refractive index (in this case, glass) to a medium with lower refractive index (in this case, water).

Snell's Law tells us that , where the i stands for incident (in this case, glass) and the r for refracted (in this case, water). We want to know when , that is, when , and this happens when the incident angle is:

Which for our values means: