Question

A light ray traveling in air enters a second
medium and its speed slows to 1.71 × 10^8 meters
per second. What is the absolute index of
refraction of the second medium?
(1) 1.00 (3) 1.75
(2) 0.570 (4) 1.94

Answer 1

Light travels at 300,000,000 meters per second, in scientific notation 3 * 10^8 meters per second. Note that in the medium it travels at 1.71 * 10^8. Taking the ratio of these two numbers with the final speed over the initial speed, we get (1.71*10^8)/(3*10^8) = 1.71/3 = 0.57

Your answer is (2) 0.570