Reflection l Two laws of reflection l Angle of incidence = angle of reflection l The angle of incidence, angle of reflection and normal all lie in the same plane
Refraction l Light travels more slowly in glass, perspex etc than in air or in a vacuum l If light meets a block of glass etc head on it goes straight through l If light meets a block of glass etc at an angle it bends
Refractive Index Light travels fastest through a vacuum l Light travels more slowly through other materials like glass, water or perspex l The Refractive Index links the speed of light in a vacuum to the speed of light in a medium l l Refractive index n = speed of light in a vacuum speed of light in the medium n = 1. 33 for water l n = 1. 5 for glass (approx – depends on the glass) l
Laws of Refraction l Law 1 Snell’s Law n= sin i sin r Law 2 The incident ray, refracted ray and normal all lie on the same plane
Relative Refractive Index l When a ray travels from one medium to another, the relative refractive index is n(first medium) n(second medium) and you use this relative n in Snell’s Law
Calculations using the laws of refraction Calculate the relative refractive index 2. Relative n = n (for first medium) n (for second medium) 3. Use the relative n in Snell’s Law to solve the problem 1.