ALSO, attempt, but do not hand in, the mock final exam. (I will go over the answers to this exam on Monday March 22.)

Question 21.8

Can a material have a refractive index less than unity? Explain.

Question 21.13

We want the reflectivity of light at normal incidence to the surface of a tranparent medium to be less than 5%. Which of the following materials listed in Table 21.1 are likely candidates: soda-lime glass, Pyrex glass, periclase, spinel, polystyrene and polypropylene?

Question 21.20

Derive Equation 21.19, starting from other expressions given in the Chapter.

Question 21.27

In your own words, describe briefly the phenomenon of photoconductivity. Would the semiconductor zinc selenide, which has a band gap of 2.58 eV, be photoconductive when exposed to visible light? Why, or why not?