(i) State the type of electromagnetic radiation, other than visible light, which is used in glass optical fibres for high-speed broadband. (ii) Give two reasons why these two types of electromagnetic radiation are used in glass optical fibres.
(i) The critical angle of the glass in an optical fibre is 42∘42^\circ42∘. Calculate the refractive index of the glass. (ii) Describe the conditions for a ray of light to undergo total internal reflection as it travels inside this glass optical fibre.
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.