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
216 exam-style questions on CIE IGCSE Physics 3.2 Light, covering 3.2.1a Reflection of light, 3.2.1b Images in a plane mirror, 3.2.2 Refraction of light, 3.2.2a Refraction of light, 3.2.2b Total internal reflection, 3.2.2c Refractive index and critical angle, 3.2.2d Optical fibres, 3.2.3a Converging and diverging lenses, 3.2.3b Ray diagrams and the nature of images, 3.2.3c Virtual images and the magnifying glass, 3.2.3d Correcting long-sightedness and short-sightedness, and 3.2.4 Dispersion of light. Each one has a worked solution and a mark scheme showing where the marks go.