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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
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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)
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
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 • 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