Alight 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

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