A reminder of the important laws of refraction Using a vacuum as medium 1 we get the absolute refractive index n of a substance: If one of the media is air we can just assume its refractive index is 1 and use these equations

refractive index of glass = 1.5 Calculate the speed of light in the glass.

(i) the angle of incidence, θ, refractive index of glass = 1.5 (b) Determine (i) the angle of incidence, θ, (ii) the refractive index of the liquid. ≈230 =1.3

Same angles as at left hand side into the air. Total internal reflection at the base of the prism

(i) the incident angle θ1, (refractive index of the glass in block 1 = 1.45) (a) Calculate (i) the incident angle θ1, θ1=22.8

n1=1.60 (refractive index of the glass in block 1 = 1.45) (ii) the refractive index of the glass in block 2, n1=1.60

θ3=59.40 usually we write in this case (iii) the angle θ3 by considering the refraction at point A. usually we write in this case θ3=59.40

In which of the two blocks of glass will the speed of light be greater? The one which has the lowest refractive index because: implies So where n is smaller c2 will be larger

c) Using a ruler, draw the path of a ray partially reflected at A on Figure 1. Continue the ray to show it emerging into the air. No calculations are expected. (2 marks) reflection at boundary with i = r refraction (at bottom surface) bending away from normal