Chapter 33 - The Nature and Propagation of Light - Problems - Exercises - Page 1106: 33.36

1.21.

Find the length for the beam traveling in air. $$3.00\times10^8m/s=\frac{L}{8.72\times10^{-9}s}$$ $$L=2.616m$$ The speed in the jelly is: $$v=\frac{2.616m}{(8.72+1.82)\times10^{-9}s }= 2.48\times10^8m/s $$ $$n=\frac{c}{v}=\frac{3.00\times10^8m/s }{2.48\times10^8m/s }=1.21$$