Reflection and Refraction

Reflection Two laws of reflection Angle of incidence = angle of reflection The angle of incidence, angle of reflection and normal all lie in the same plane

Refraction Light travels more slowly in glass, perspex etc than in air or in a vacuum If light meets a block of glass etc head on it goes straight through If light meets a block of glass etc at an angle it bends

Refractive Index Light travels fastest through a vacuum Light travels more slowly through other materials like glass, water or perspex The Refractive Index links the speed of light in a vacuum to the speed of light in a medium Refractive index n = speed of light in a vacuum speed of light in the medium n = 1.33 for water n = 1.5 for glass (approx – depends on the glass)

Laws of Refraction Law 1 Snell’s Law Law 2 The incident ray, refracted ray and normal all lie on the same plane n = sin i sin r

Relative Refractive Index 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 1. 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