A ray of light travelling in air strikes a block of acrylic plastic at an angle of 40∘40^\circ40∘ to the normal. The light slows down as it enters the plastic block.
State and explain, in terms of wavefronts, what happens to the light.
The speed of light in this acrylic plastic block is 2.1×108 m/s2.1 \times 10^8\text{ m/s}2.1×108 m/s. The speed of light in vacuum (or air) is 3.0×108 m/s3.0 \times 10^8\text{ m/s}3.0×108 m/s.
Calculate the refractive index of the acrylic plastic.
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.