Practice portal › Ray Optics and Optical Instruments › Refraction through a Prism
Asked in GSEB Board March 2022 · Dispersion and scattering
Given: the secondary rainbow.
Idea: follow one ray through a raindrop and count the reflections — it refracts in, bounces off the inside of the drop some number of times, and refracts out.
Primary bow: refraction, 1 internal reflection, refraction. It sits about 42° from the antisolar point, red outermost.
Secondary bow: refraction, 2 internal reflections, refraction. It sits further out, at about 51°.
The extra reflection turns the colour order over, so the secondary bow has red innermost, and it is dimmer because light is lost at every reflection.
So a secondary rainbow needs 2 internal reflections.
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