Hi,

 

I understand how a rainbow is created through dispersion of light etc. But I was just wondering how does the physics explain the curvature of the rainbow. Why isn't it just a straight rainbow?

 

Thanks

 

Jd

Hi' date='

 

I understand how a rainbow is created through dispersion of light etc. But I was just wondering how does the physics explain the curvature of the rainbow. Why isn't it just a straight rainbow?

 

Thanks

 

Jd[/quote']

 

It's actually refraction and reflection of light through water droplets. Refraction angle depends on wavelength, so that splits the white light up. The rainbow is curved because, in order for an observer to see any particular color, the light must come in at a given angle. The projection of that is a cone, and the base of a cone is a circle. You only see half because the ground gets in the way (people in airplanes get to see whole circles) and the shadow of your head is at the center of the circle. More on rainbows.

on certain occasions this general phenomenon is surpassed in the form of a "sun dog" a rainbow around the Sun in a complete circle, like a halo

a very beautifull but rare occurance in the UK, I`ve seen one only once on Shell Island in Wales, but many of them when I lived in Canada.

water falls will often have the same effect too in bright sunlight at certain angles.

the "pot of Gold" at the end of the rainbow is bogus though, I tried it as a kid, I got a vanilla ice cream for my efforts though from the lady in the ice cream van that I asked

on certain occasions this general phenomenon is surpassed in the form of a "sun dog" a rainbow around the Sun in a complete circle' date=' like a halo

a very beautifull but rare occurance in the UK, I`ve seen one only once on Shell Island in Wales, but many of them when I lived in Canada.

water falls will often have the same effect too in bright sunlight at certain angles.

[/quote']

 

Also known as a 22 degree halo. It's caused by ice crystals in the upper atmosphere. I've seen a couple - yeah, they're pretty neat.

I once saw a moon-rainbow. eerie.

those are REALLY RARE