LilWabbit
Senior Member
From the same Physics Stack Exchange discussion cited earlier on the first page of this thread:
This is pretty much basics and identical to what @Ann K recaps here:
But the author continues with droplet size and droplet density as additional criteria:
That's an opinion based on an assumption of alignment of some but not all the rainbow criteria mentioned in the foregoing.
And once again: Even if there were a huge contiguous geographic zone optimal for viewing a rainbow by millions of people at around Tallahassee, it doesn't really address in any helpful way the probability of a rainbow appearing at Buckingham Palace .
Article: There are many obvious reasons why rainbows are not very common or, more precisely, are not very commonly observed by any particular individual: it has to be rain, it has to be sun, it has to be this or that part of the day, East or West, dark background, etc. and that individual has to be in the right spot at the right time and actually look.
This is pretty much basics and identical to what @Ann K recaps here:
If you'll permit a childish simplification, here's a quick and dirty sketch made from the weather map of the USA yesterday. The essential requirements are rain, the end of the cloud cover, and the sun low enough to come underneath. It wasn't a completely solid rain cloud, but fairly close.
But the author continues with droplet size and droplet density as additional criteria:
Article: If all those other things line up, will we always see a rainbow or does it have to be a particular type of rain or particular type of water droplets? Here are couple of additional factors affecting the probability/visibility of a rainbow:
Droplet size and shape. For the brightest rainbow, droplets have to be 1-2mm. Droplets smaller than 0.05mm will create a white rainbow, etc. More details could be found here.
Droplets density. For the rainbow to work, a photon has to hit one droplet and fly right back to your eye, i.e., it has to be scattered once. If the density of droplets is high, like in clouds, a photon will likely hit multiple droplets and end up moving at a random angle, breaking the 42 degrees requirement.
But ... this one particular band stretched from Tallahassee, Florida to Washington DC at the time I looked at the weather map, roughly a distance greater than Land's End to John O'Groats, and rainbows would have been in sight of many, many millions of people, had they looked out the window.
That's an opinion based on an assumption of alignment of some but not all the rainbow criteria mentioned in the foregoing.
And once again: Even if there were a huge contiguous geographic zone optimal for viewing a rainbow by millions of people at around Tallahassee, it doesn't really address in any helpful way the probability of a rainbow appearing at Buckingham Palace .
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