A hiker stands on an isolated mountain peak near sunset and observes a rainbow formed by water droplets in the air 8 km. away. The valley is 2 km. below the mountain peak and entirely flat. What fraction of the complete circular arc of the rainbow is visible to the hiker? I tried to solve the problem with the fact that the deviations of red light and violet light are 42 and 40 degrees resp. I got the width of the rainbow he sees as 8tan42-8tan40 = 0.49 But what is the total width?