Rainbow Visible to Hiker on Isolated Mountain Peak: 0.49 Fraction

  • Thread starter Thread starter Abhishek.S
  • Start date Start date
  • Tags Tags
    Optics
Click For Summary
SUMMARY

The discussion centers on a hiker observing a rainbow from an isolated mountain peak, calculating that the visible fraction of the rainbow's arc is 0.49. The hiker uses the deviation angles of red light (42 degrees) and violet light (40 degrees) to determine the width of the rainbow. The calculation involves the formula 8tan42 - 8tan40 to find the visible portion. The conversation also touches on the philosophical aspect of the rainbow's existence, emphasizing that it is perceived individually by each observer.

PREREQUISITES
  • Understanding of light refraction and dispersion
  • Familiarity with trigonometric functions, specifically tangent
  • Basic knowledge of geometry related to circular arcs
  • Concept of observer-dependent phenomena in optics
NEXT STEPS
  • Study the principles of light refraction and dispersion in detail
  • Explore advanced trigonometric applications in physics
  • Research the geometry of circular arcs and their properties
  • Investigate the philosophical implications of perception in optics
USEFUL FOR

Physics enthusiasts, optical scientists, hikers interested in natural phenomena, and anyone exploring the intersection of perception and reality in visual experiences.

Abhishek.S
Messages
2
Reaction score
0
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?
 
Physics news on Phys.org
I just want to mention first that stating that the rainbow forms at a distance of 8 km is a bit artificial, since it really forms at infinity (Well actually there is nothing out there, the rainbow forms on your retina, so each observer has his own personal rainbow inside of his eye! But if you were to stand next to me and I say "Do you see the rainbow there?" you would agree with me. Another observer flying over us in his airoplane would actually see the rainbow as a circle in another place. You can even photograph it and it will appear on the film, so we all say seeing is believing, but it still isn't actually out there! Some people might disagree with this statement of mine, this is my personal view on the subject. It makes you think doesn't it?), but that aside with the given info one can calculate the radius of the red circle of the rainbow at this distance, r_r. That enables you to evaluate the angle \alpha that is cut off by the horizon from this circle and finally the arc that is below the horizon s_{below}.

There probably is a much more elegant way of calculating this, but for now it eludes me.
 

Attachments

  • rainbow.gif
    rainbow.gif
    10.7 KB · Views: 794
Last edited:

Similar threads

Rainbow Arc Fraction: Solve the Math Problem
  • · Replies 3 ·
Replies
3
Views
2K