Two parallel rays of light, one red and one blue, enter a glass prism. Fig. 4.1 shows both rays of light before they enter the prism. The blue ray is also shown incident on a different side of the prism after passing through the prism. The ray of blue light strikes the left side of the prism at an angle equal to its critical angle c.[Figure 4.1 (not to scale)]

1. (a)(i)On Fig. 4.1, mark and label the angle of incidence i and the angle of refraction r for the blue light as it enters the prism.[1]
2. (a)(ii)On Fig. 4.1, continue the path of the blue light after it strikes the left side of the prism.[1]
3. (a)(iii)The refractive index of glass for red light is smaller than the refractive index for blue light. On Fig. 4.1, draw the path of the red light as it travels in the prism and after it strikes the left side of the prism.[2]
4. (b)(i)State what is meant by the critical angle.[2]
5. (b)(ii)The refractive index of glass for blue light is 1.5. Calculate the critical angle c for blue light in glass. Show your working.[2]

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