| Reply to Thread New Thread |
|
|
08-17-2012, 02:55 AM
|
#1 |
|
|
 3 Rainbow Questions
Saw a rainbow today
a really intense one, very colorful and a full arc it also had a second one around it but less intense so I was wondering, why is there is second one? how wide are rainbows? how high are rainbows? |
|
|
08-17-2012, 02:57 AM
|
#2 |
|
|
Saw a rainbow today |
|
|
|
08-17-2012, 02:57 AM
|
#3 |
|
|
how wide are rainbows?
how high are rainbows? depends on how far away the rain is from you. i've seen them end just in front of my car as i'm driving. or appear to be there. |
|
|
|
08-17-2012, 05:13 AM
|
#4 |
|
|
> why is there is second one?
The main one comes from light bouncing once inside each raindrop. The secondary rainbow comes from light bouncing twice inside each raindrop. > how wide are rainbows? The main one is 1.6 degrees wide, (2 degrees according to other websites). The secondary one is roughly 3 degrees wide. Does anyone have more accurate data than that? > how high are rainbows? 41 degrees from the Sun (or other light source) for the primary bow and 51.5 degrees from the Sun for the secondary bow. At a rainstorm distance of say 5 to 10 km, that gives a maximum height for the primary bow (at sunset) of 4.5 to 8 km. But when the Sun is at say 20 degrees above the horizon that drops to 2 to 4 km high. Height of rain-clouds matters as well. Rain storms from rain clouds may only be about 2 km high, although some are higher and lower. The rainbow forms only below the rain-clouds. |
|
|
|
08-17-2012, 05:31 AM
|
#5 |
|
|
Saw a rainbow today Truly spectacular. |
|
|
|
08-17-2012, 06:06 AM
|
#6 |
|
|
This doesn't answer your question, but I was in England a few years ago and at the White Cliffs of Dover saw 22 rainbows in the sky at once. |
|
|
|
08-17-2012, 06:34 AM
|
#7 |
|
|
wow! I'd kill to see that
 This doesn't answer your question, but I was in England a few years ago and at the White Cliffs of Dover saw 22 rainbows in the sky at once. |
|
|
|
08-17-2012, 06:48 AM
|
#8 |
|
|
What was the light sources? A rainbow is always antipodean to the light source, and at best you might see three on a single rain front using the sun as the source (with two and three each being less intense). I guess it is possible to have a secondary rain front behind the first, but 22 seems like there must be multiple artificial sources. |
|
|
|
08-17-2012, 04:44 PM
|
#9 |
|
|
"22 rainbows" sounds not like rainbows, but like a complex halo display. As was observed in the other place the tertiary and quaternary rainbows (which are towards the Sun, not towards the anti-solar point) have only just been photographed for the first time. The fifth rainbow (back towards the primary and secondary) is thought to be too weak to ever observe at least unaided.
You can get a reflection rainbow, but even if you get a reflection from both primary and secondary that leaves only four that you could ever expect to see at once. |
|
|
|
08-17-2012, 04:49 PM
|
#10 |
|
|
When moll says "41 degrees from the Sun" he means "41 degrees from the antisolar point" of course - that is the rainbow angle giving the radius of the bow. If the rainbow occurs right on sunset then the Sun will be on the horizon and the antisolar point on the opposite horizon and so the top of the bow will be 41 degrees above the horizon. In principle you could see the upper part of the bow created from sunlight coming from just below the horizon (and the antisolar point just above it) so the maximum elevation of the top of the bow could be a bit above 41 degrees above the horizon. In practice though almost all rainbows are seen a before sunset and so the maximum elevation will be less than 41 degrees.
The angular width of the bow varies a little due to drop size, I believe (with larger spreading due to diffraction in smaller drops). I could check later. |
|
|
|
08-17-2012, 04:52 PM
|
#11 |
|
|
The rainbow, of course, is an image (a highly distorted image of the Sun) so the actual location (distance, height etc) of the mirror (ie the raindrops) does not affect the geometric properties of the image. It does, however, affect our psychological perception of the image eg that weird sense when you pass through the mirror reflecting an image at optical infinity.
|
|
|
|
08-17-2012, 08:29 PM
|
#12 |
|
|
The dark area between the primary and secondary bows is caused by the light being reflected away from the observer by raindrops in that area. It is called Alexander's dark band (not Alexander's ragtime band which would be more fun).
|
|
|
|
08-17-2012, 08:52 PM
|
#13 |
|
|
The dark area between the primary and secondary bows is caused by the light being reflected away from the observer by raindrops in that area. It is called Alexander's dark band (not Alexander's ragtime band which would be more fun). 
|
|
|
|
08-17-2012, 08:57 PM
|
#14 |
|
|
"the light being reflected away from the observer by raindrops in that area"
Well, the light is reflected away from that area by all of the raindrops in the shower, not just those in that particular angular region. the point is that the geometry of the reflection means that (essentially) no light from anywhere can be reflected into that region. |
|
|
|
08-17-2012, 08:59 PM
|
#15 |
|
|
and since it is a new forum I guess we can be generous and credit that as a new joke from steve
|
|
|
|
08-18-2012, 01:38 AM
|
#16 |
|
|
>>>You have got to be kidding. How many years have you been on this forum...
yeah, been on a while but I do forget things people do forget things.... |
|
|
|
08-18-2012, 02:24 AM
|
#17 |
|
|
>>>You have got to be kidding. How many years have you been on this forum... |
|
|
|
08-22-2012, 02:55 AM
|
#18 |
|
|
I saw this arc at 8.00am this morning, directly overhead. It lasted about 10 minutes.
|
|
|
|
08-22-2012, 03:00 AM
|
#19 |
|
|
|
|
|
|
08-22-2012, 04:06 AM
|
#20 |
|
|
I saw this arc at 8.00am this morning, directly overhead. It lasted about 10 minutes. |
|
|
| Reply to Thread New Thread |
«
Previous Thread
|
Next Thread
»
Hybrid Mode
| Currently Active Users Viewing This Thread: 5 (0 members and 5 guests) | |
|
|
