How Rainbows Form

The physics behind rainbows and surprising facts about rainbows.

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Many thanks to the VlogBrothers for their sponsorship of this video.

Music - Rhythm Changes

[znhrvth]

Well, if you have a physics / math background and you know more or less how rainbows are formed this video is a great way to refresh your memory. For everyone else explaining the phenomenon in 3 minutes may be a bit fast.

[johnnyallen]

Great I’m more confused than when I originally looked this up

[vasamoradora]

"NOW THE STORY IS COMPLETE"
But i still cannot get anything...

[JohnPaquette]

BEST explanation I have found, after hours of searching! And in UNDER 4 MINUTES. Mind blown.

[codzomz]

Hey physics Girl, I fly in the airlines and I see all types of rainbows all the time... Have you ever heard of a "glory"? This is the effect of refraction when looking down at a cloud from a plane and what is really cool is that you can see where you are sitting in the plane from said rainbow, as all glories centralize around your position in reference to your seat... Pretty cool stuff!

[StephenJordanJavaKrypt]

I've seen many double rainbows, and noticed that the sky appears darker above the rainbow and brighter in the arc, but I've never noticed the 2nd rainbow is flipped order. I'll pay closer attention next time. Thanks!

[ScienceAsylum]

I've been meaning to do a video on this. You beat me to it! ...and I think you probably did a better job than I would have.  I love the elaboration about the multiple colors and max angles at the end.

[seagullsg]

That was cool. Knew rainbows had to be complete circles, how could it be otherwise but never noticed the colours in a double rainbow are flipped. Blew my mind, really enjoyed the explanation

[nymeria]

Genuinely so fascinating! I never knew the details beyond light refracting through droplets, but this makes rainbows even more incredible.

[SenpaiSan]

The maximum angle made by a light ray with the normal of a surface to accomplish refraction is called critical angle. If the angle is made greater than this point it would reflect. This phenomenon is also called total internal reflection(TIR).
Anyways thanks a lot for your explanatory videos

[BlimeyGeezaMate]

Complex as hell but you really broke it down nicely! I'd love to see more of this with other physical explanations too

[MrOvipare]

ahah "The End", that was cute.
Good explanation! Cool animations

[wojja]

There Are also some further effects from DIFfraction as well as the REfraction mentioned here. These show up when the raindrops are quite small and mostly the same size.

[adrianjw]

42° is the max angle... no wonder why 42 is "the answer to life the universe and everything"  :D

[Nocturnal_lizzart]

i feel so much smarter knowing this, now i can impress my friends whenever they ask how a rainbow works ahahah thank you:)xx

[NTeamEN]

Whenever someone tells that I haven't been told the full story I'm like "yeah right" but this was actually mind blowing (especially the part about light hitting the drops of water in all the different directions).
Great work :)

[deltaray]

I'm surprised she didn't use this video to reveal she is from Hawaii. Hawaii has a high incidence of rainbows. I saw on average 3 per day there where as back in the midwest I may see 3 per year. After she spent a lot of time in Boston at MIT she probably realized how rare they are other places.

[FMuscleZ]

I have seen full circle rainbows while skydiving on a partially cloudy day. They formed over the clouds as I was free diving.

[GelidGanef]

Everytime I see one of your videos in my feed I'm like, "That's so stupid, I've known how that works since grade school." And then I actually watch and learn all these things I've never heard of before. And all the half-explanations I got of that thing before that just left me kind of confused, they sound pretty stupid once I've heard you explain it better.

Thanks for keeping things simple without dumbing them down :) 

[XMostaxX]

The video is great! There is one tiny mistake though, the red light should be at the bottom of the spectrum after the first phase of refraction at 3:25, since it bends the least as it is fastest.
After reflection 1 around the normal, the red light gets from the bottom to the top of the spectrum (which is depicted correctly in the video), then gets reflected again around the normal, where it goes from the right to the left of the spectrum (also depicted correctly in the video).