Must the sun be at your back in order for you to see a rainbow?

Question

It was a Crainium question, and they said the answer was TRUE. But, that doesn't seem right, does anybody know?

Answer 1

Actually...it is true...Three factors must be in place for you to see a rainbow. First, the sun must be shining (duh!). Second, the sun must be behind you, and third, there must be water drops in the air in front of you. Sunlight shines into the water drops, which act as tiny prisms that bend or "refract" the light and separate it into colors. The drops actually bend the light twice and it is after the second bend, we see the rainbow. Surprisingly enough, each drop reflects only one color of light, so there must be many water drops to make a full rainbow. You'll notice that you can see the brightest rainbows when the water drops are large, usually right after a rain shower. The reason the rainbow is circular is because when a raindrop bends light, that light then exits the raindrop at an angle 40 to 42 degrees away from the angle it entered the raindrop. This also explains why the rainbow appears to be curve,as you can only see the beams of light from raindrops that are 40 to 42 degrees away from the shadow of your head. Help any?

Answer 2

A rainbow is formed by sunlight REFLECTING from the INSIDE of raindrops (as opposed to passing through [see below]).  In order for the rainbow to form, the reflection MUST be in a rather narrow band around 42 degrees.

So YES, the sun MUST be behind you, and it must be in a 42-degree relationship with you and the raindrops in front of you.

But there is also a thing called the PRISMATIC EFFECT.  This concerns light TRANSMITTED (passing through, not reflecting) a clear substance, like water droplets or ice, and the light source (sun, moon, or a lightbulb) must be in FRONT of you.

With a prismatic effect, you will most often see a colored HALO around the light source.  This most often happens in winter, when ice crystals in the air cause a halo around the moon.  This can happen during the daytime, usually in the very coldest winters when snow is blowing.  It can also happen during a rain or snoew storm, and you will see halo's around street lights.

The difference, of course, is that a HALO is circular, but a rainbow is not -- AND that for a true rainbow the sun MUST be behind you.

Answer 3

No, a rainbow is actually an optical ellusion, as you move it moves.http://www.weatherwizkids.com/optical_il...

Answer 4

Rainbows occur when light passes through water vapor at certain angles.  You more or less just have to be at the right spot at the right time.  To answer your question though, no, the sun does not have to be at your back.

Answer 5

The center of the arc formed by the rainbow is on line formed from the sun to the observer and on to the rainbow. Yes, the sun must be behind you to get this straight line with you in the middle. (Note: the straight line goes to the center of the arc of the rainbow - the higher the sun, the lower the rainbow)

Answer 6

It's not as straight-forward as "true" or "false". In a way it is only visible when the sun is at your back, then what happens if you pivot to the left or right by 90 degrees? The rainbow is still there, but the sun is no longer at your back; however, it will be at the back of your head. So if you're looking at a rainbow straight-on (which is not often the case), then the sun would be behind your back.

Answer 7

the sun can be any where except in front of you.  

Answer 8

no its not true