1. Reflection and Refraction

2. 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

3. 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

4. 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)

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

6. 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

7. Calculations using the laws of refraction • Calculate the relative refractive index • Relative n = n (for first medium) n (for second medium) • Use the relative n in Snell’s Law to solve the problem