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Author Topic: Why do rainbows only appear for a short period of time?  (Read 7269 times)

Offline Chemistry4me

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This morning I saw one and it couldn't have lasted more than 8 minutes, so why do we I at least not see rainbows which last say half an hour?


 

Offline Karen W.

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Why do rainbows only appear for a short period of time?
« Reply #1 on: 11/05/2009 08:24:30 »
I have never thought about that! That is a good question but as I recall several times at the preschool we had seen them last at least 20 minutes most of the way through our group and outdoor activity before free play maybe longer...but I never thought to time it!
 

Offline dentstudent

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Why do rainbows only appear for a short period of time?
« Reply #2 on: 11/05/2009 08:45:48 »
Assuming that this is a sun-formed rainbow - as long as the sun is up, that it is shining through rain, and that you are at the angle required to see the light refraction within the raindrops, I guess that there is no time limit to how long you can see a rainbow for. They are rather ephemeral because of one of the three variables above changing, and stopping the show.
 

Offline Chemistry4me

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Why do rainbows only appear for a short period of time?
« Reply #3 on: 11/05/2009 09:01:30 »
So theoretically they can last hours eh?
 

Offline Chemistry4me

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Why do rainbows only appear for a short period of time?
« Reply #4 on: 11/05/2009 09:05:51 »
That is a good question but as I recall several times at the preschool we had seen them last at least 20 minutes
Now that I think about it, the rainbow appeared for about 7 minutes and then it disappeared for about 2 and then it appeared again for about another 4 minutes.
 

Offline dentstudent

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Why do rainbows only appear for a short period of time?
« Reply #5 on: 11/05/2009 09:16:43 »
So theoretically they can last hours eh?

I guess so - if you are able to maintain the critical angles...
(diagram from http://www.photocentric.net/rainbow_angles.htm)
 

Offline Karen W.

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Why do rainbows only appear for a short period of time?
« Reply #6 on: 11/05/2009 09:46:20 »
Well thats interesting....C4M..I have never seen one do that.....so when it disappeared does that mean one of the elements changed temporarily..then started back up again when it returned to the same conditions?
 

Offline Chemistry4me

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Why do rainbows only appear for a short period of time?
« Reply #7 on: 11/05/2009 09:57:20 »
Yeah, I guess the Sun might have gone behind a cloud for those moments, because it certainly was raining!
 

lyner

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Why do rainbows only appear for a short period of time?
« Reply #8 on: 11/05/2009 17:21:02 »
It needs to be raining (with fairly big drops, I think - for a bright bow) in half of the sky and the background should be fairly dark, to get a good contrast for the bow to appear in front of. It must also be clear in the direction where the Sun is. If there is any wind, this situation will be fairly rare because clouds will obscure the sun and a blue sky background will dilute the rainbow.
 

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Why do rainbows only appear for a short period of time?
« Reply #8 on: 11/05/2009 17:21:02 »

 

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