A manufacturer is choosing a transparent resin for a flat illuminated panel. Light travels inside the panel and meets a resin–air boundary. Both resins are more optically dense than air.
| resin | critical angle |
|---|---|
| P | 42∘42^\circ42∘ |
| Q | 49∘49^\circ49∘ |
The ray meets the boundary at an angle of 44∘ 44^\circ\,44∘ to the surface. The light needs to remain inside the panel by total internal reflection.
Explain which resin should be used.
Calculate the angle between the incident ray and the reflected ray when the resin you selected in (a) is used.
93 exam-style questions on Edexcel GCSE Physics 5.1 Reflection, refraction and lenses, covering 5.1.1 Reflection, refraction and total internal reflection, 5.1.2 Specular and diffuse reflection, 5.1.3 Colour of light: absorption and filters, 5.1.4 Lenses: power, focal length and shape, 5.1.5 Ray diagrams for converging and diverging lenses, and 5.1.6 Real and virtual images. Each one has a worked solution and a mark scheme showing where the marks go.