A ray of light travels from a medium of refractive index n1 n_1\,n1 towards a boundary with a medium of refractive index n2n_2n2. Which set of conditions is necessary for total internal reflection to occur at the boundary?
n1>n2n_1 > n_2n1>n2 and the angle of incidence is less than the critical angle
n1>n2n_1 > n_2n1>n2 and the angle of incidence is greater than the critical angle
n1<n2n_1 < n_2n1<n2 and the angle of incidence is less than the critical angle
n1<n2n_1 < n_2n1<n2 and the angle of incidence is greater than the critical angle
100 exam-style questions on CIE IGCSE Physics 3.2.2 Refraction of light. Each one has a worked solution and a mark scheme showing where the marks go.