An engineer tests the transparent core of an optical fibre. The core is more optically dense than the air around it, and the critical angle for the core–air boundary is 39∘39^\circ39∘. Two rays, J and K, travel through the core and meet the boundary.
| ray | angle between the ray and the boundary surface |
|---|---|
| J | 51∘51^\circ51∘ |
| K | 39∘39^\circ39∘ |
Which statement describes what happens to rays J and K at the boundary?
J: total internal reflection occurs; K: the refracted ray travels along the boundary
J: the refracted ray travels along the boundary; K: the refracted ray travels along the boundary
J: the refracted ray travels along the boundary; K: total internal reflection occurs
J: total internal reflection occurs; K: total internal reflection occurs
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.