Saturday 25 January 2020

optics - Why aren't rainbows blurred-out into nothing after they are produced?


I understand how a prism works and how a single raindrop can scatter white light into a rainbow, but it seems to me that in normal atmospheric conditions, we should not be able to see rainbows.



enter image description here


When multiple raindrops are side-by-side, their emitted spectra will overlap. An observer at X will see light re-mixed from various originating raindrops. The volume of rain producing a rainbow typically has an angular diameter at least as wide as the rainbow itself, does it not?


So why can we still see separate colours?


EDIT: To emphasise the thing I am confused about, here is a rainbow produced from a single raindrop...


enter image description here


...here are the rainbows produced by two raindrops, some significant distance apart...


enter image description here


...so shouldn't many raindrops produce something like this?


enter image description here


I will accept an answer which focuses on this many-raindrops problem, I will not accept an answer which goes into unnecessary detail as to how a single raindrop produces a rainbow.





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