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JDK1.0.2 simulations (1996-2001) => Optics => Topic started by: Fu-Kwun Hwang on January 29, 2004, 10:39:38 pm

Title: physics of Rainbow
Post by: Fu-Kwun Hwang on January 29, 2004, 10:39:38 pm
A most charming example of chromatic dispersion is a rainbow.
When white sunlight is intercepted by a drop of water in the atmosphere, some of the light refracts into the drop, reflects from the drop's inner surface, and then refracts out of the drop.
As with the prism, the first refraction separates the sunlight into its component colors, and the second refraction increases the separation. The result is the rainbow.

You can find similar explanations at textbook. However, the incoming ray can be refracted at different angle, why the rainbow is located at fixed angle of view? Why it is a circle?

This applet shows the physics of the rainbow.

The black circle represents a drop of water in the atmosphere.
Initially, red light is coming from the left; you can click inside the colored blocks to change the color of the incoming light.
The incoming ray is unpolarized, which can be represented as a mixture of two polarized waves whose planes of polarization are perpendicular to each other.
So the notation " 50%| 50%+" means that half is polarized in the up-down direction and half is perpendicular to the screen.
Many things can happen to the light.
• Part of the incoming ray is reflected back to the atmosphere (indicated by ray number 1). The intensity of each polarized component is shown along the ray path.

• Part of the light refracts into the drop, then refracts back to the atmosphere(ray number 2).

• Some reflects from the drop's inner surface, and refracts back to the atmosphere (ray number 3). This gives rise to the ordinary rainbow.

• Some reflects twice inside the drop, then refracts back to the atmosphere.(ray number 4) This gives rise to the secondary rainbow that is sometimes seen.

You can drag the incoming ray, move it up and down, and watch how the relative intensities change. R is the radius of the water drop; b is the vertical distance of the incoming ray from the center of the circle.
The intensity of the light coming from rays 3 and 4 is plotted versus viewing angle. Click ^or vto change the scale.
For ray number 3 there is a maximum scattering angle, and for ray number 4 there is a minimum -- this is why there are strong peaks in the scattered intensity.
The rainbow is actually a disk of scattered light, but it is brightest at the edge; the disk for different wavelengths is a different size, and that is why we see the color effects there.
You can click inside the white box, and see what will happen to white light.
When light refracts, it follows the law of refraction   ni sin(ctai)=nr sin( ctar) where n is the index of refraction.
The number in the left-bottom corneri is the angle of incidence, r is the angle of refraction.
Most of the light is refracted out by ray
2. When your eyes intercept the separated colors from raindrops, the red you see comes from drops angled slightly higher in the sky than does the blue.
You see a circular arc of color, with red on the outside and blue on the inside.
Click inside the colored box to show this effect. You can drop one of the rain drops,Try it!

Did you notice that the rainbow consists of partially polarized light?
The following picture are results from experiment (view rainbow with polarizer at different angle).

You are welcomed to check out EJS version of rainbow applet (http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1430.).

Title: Email discussion
Post by: Fu-Kwun Hwang on January 29, 2004, 10:41:06 pm

 name direction of electric field color s-wave perpendicular to the screen ( + ) same color as the light p-wave  in the up-down direction ( | ) yellow

This is an e-mail message from Neal Rasmussen (posted with his permission)

I am a tornado chaser for 20 years. About 4 years ago I was driving through a McDonald's drive thru. As it was just after a pretty good storm, I had mys polarized yellow tinted flip-up sunglasses on. Low and behold I almost dropped my cigarette into my lap. There off in the east was a double rainbow! Not the kind I've seen dozens of times where the second one is reveresed and much outside the primary, but this was immediatly INSIDE the primary!

Gaping with my mouth open and people behind me honking, I flipped my flip-ups up and the second inner one went away! I must have sat there for 2 minutes flipping my sunglasses. The colors were NOT reversed and it looked like one continuous double wide rainbow, with two complete sets of colors. I ruled out that the flip-ups where giving double vision as I looked at lights the next day, streetlights headlights, etc. and no doubles! Can this possibly be? Could a source of polarized light be at a different angle, perhaps the sun shining through a cirrus cloud or noctelucent (sp).

Email message:
Subject: circular rainbows
Date:     Fri, 4 Aug 2000 19:03:52 EDT
From:    Jrs3290@aol.com
To:        hwang@phy03.phy.ntnu.edu.tw

Hi, I am facinated by rainbows but am not smart enough to understand it all.
I do know that the most amazing one I have ever seen was when I was in a
small single engine aircraft above a layer of white clouds.  The cloud cover
was smooth and the sun made a shadow of my aircraft .  As I looked at the
shadow of the aircraft on the clouds I noticed it was encircled by a
circular rainbow. The rainbow followed until the cloud cover changed and then
disappeared.  Sincerly, Jim Spencer

My response:

I was always dreaming to be able to see the same view as you have seen (whenever  was on  an airplane).
What you have seen is a true rainbow. Circular rainbow can only be viewed from above the ground.
When we were on the ground, at least half of them were missing.
The viewing angle is about 42 degree.

Subject: Re: circular rainbows
Date:     Sat, 5 Aug 2000 10:47:47 EDT
From:    Jrs3290@aol.com
To:        hwang@phy03.phy.ntnu.edu.tw

Hi, yes you may use the letter any way you like.  If you do I wish you would
let me know so I can look at it.  The angle from where I was sitting in the
aircraft and the shadow was about 45 degrees as I remember it and I wonder if
the angle had been greater or less do you think I would still have seen a
rainbow or was I just fortunate that day to be at the right place at the
right time ??  Jim Spencer

Title: topic44
Post by: on January 30, 2004, 08:09:50 am
Subject: I saw a Polarized Rainbow!
Date: Sat, 14 Mar 1998 01:18:24 -0800
From: Neal Rasmussen <nealras1@airmail.net>
To: hwang@phy03.phy.ntnu.edu.tw
I am, as far as I know, the first to see a "Polarized Rainbow"!
I think we should name this phenomona the "Rasmussen-Wang Rainbow". :-)
I am a tornado chaser for 20 years. About 4 years ago I was driving through a McDonald's drive thru.
As it was just after a pretty good storm, I had mys polarized yellow tinted flip-up sunglasses on.
Low and behold I almost dropped my cigarette into my lap.
There off in the east was a double rainbow!
Not the kind I've seen dozens of times where the second one is reveresed and much outside the primary,
but this was immediatly INSIDE the primary!
Gaping with my mouth open and people behind me honking,
I flipped my flip-ups up and the second inner one went away!
I must have sat there for 2 minutes flipping my sunglasses.
The colors were NOT reversed and it looked like one continuous double wide rainbow,
with two complete sets of colors.
I ruled out that the flip-ups where giving double vision as I looked at lights the next day,
streetlights headlights, etc. and no doubles!
Can this possibly be? Could a source of polarized light be at a different angle,
perhaps the sun shining through a cirrus cloud or noctelucent (sp).
Neal Rasmussen nealras1@airmail.net

Title: topic44
Post by: on January 30, 2004, 04:38:12 pm
From: NAPLES96@aol.com
Date: Thu, 28 Oct 1999 08:58:38 EDT
Subject: Interesting find!
To: hwang@phy03.phy.ntnu.edu.tw

Just stumbled upon your observation while looking for reasons for a rainbow.
Actually I had seen a "round" rainbow and was unable to find any comments on
the subject.  Have you any knowledge of one?

I'm just an admirer of the beauty of the sky, here in Naples, FL.

Thank you,

Title: topic44
Post by: on January 30, 2004, 04:49:45 pm
From: Ayuyroq@aol.com
Date: Thu, 2 Dec 1999 16:48:07 EST
Subject: (no subject)
To: HWANG@phy03.phy.ntnu.edu.tw

My youngest daughter did an elementary school science fair project on the
effects of pollution on rainbows and she found the applet on how rainbows are
formed, which is copyrighted by you, on line.

Could you tell us how to credit this work done on line in her Bibliography?

Thank you,

A.

Title: rainbow physics
Post by: on February 22, 2004, 11:34:00 am
Great site with clear explanation.

I thought the double rainbow that one sees emanates from light that enters very low on the raindrop and then reflected twice within the raindrop.  Is that true?

Your diagram seems to suggest that the primary and secondary rainbows are created by different paths of the same light and not seperate rays of light.

Is there any way to add the perspective of the observer to your diagram to show the paths of the light producing what the observor sees (primary and secondary rainbows) and the angles at which the rainbows would be seen in nature.

Is there anyway to also add the perspective of the observer to show why the color spectrum is seen as a "bow" or arc and why a rainbow would be seen as a circle from just the right perspective (e.g. airplane).

Great site and thanks.

Title: topic44
Post by: Fu-Kwun Hwang on February 22, 2004, 11:45:13 am
from the following picture, you will find that the intensity of the first rainbow is about 2*4.5% of the incoming red light. So the intensity is indeed small.
The rainbow you saw was coming from many different raindrop.
The primary and the second rainbow also create from differnet raindrop and different light path. Remember light need to enter your eye for you to see the image.
The angle shown on the applets is assume the sun light is horizontal.
If the sun is higher you need to substract the angle of the sun ray relative to horizontal.
If the angle is less than zero , you would not be able to see rainbow on the ground.
That why you never saw rainbow at noon (after 9am or  before 3pm)  on the ground.

The angle for the second also shown on the applet, as indicated in the following picture.

The following applet show you why why the color spectrum is seen as a "bow" or arc.
(The other half  will be underground if there are raidrops and can refelect sun light, which is impossible.) However, it is possible when you were on an airplane.

Title: topic44
Post by: Rainbow_Zanadar on February 22, 2004, 08:43:38 pm
Nice explanations of the mathematics of rainbows.

A "Round" Rainbow will always be observed when the sun is directly behind you and the water droplets are directly in front of you and you are at an altitude that enables you to see the circle of light. I'm not entirely sure if the distance you are from the water droplets determines the size of the circle, I'll have to investigate more.  The "circle" is a "Halo" effect similar to the effect you get on a foggy night when the moon is at its fullest.

Title: topic44
Post by: Le on October 10, 2005, 09:59:27 pm
Hi!

Came across this site when researching light and the rainbow. Have found some really interesting information here. I dont actually work in or study science, but I am fascinated by it and always trying to inform myself in many scientific theories which I try to incorporate into my artwork(am in my final yr in art college, specializing in interdisciplinary studies). Anyway...
:oops: This will possibly be a stupid question but its something someone has recently told me about. I have been told that on one side of the rainbow there is a kind of blank space or void which is said to be unexplanable, romantically described as holding the mysteries of the universe, this fascinated me so much and am wondering if there is infact such a void?...

Thanks

Title: email from users
Post by: Fu-Kwun Hwang on February 25, 2006, 04:03:41 pm
I receive the folllowing message from a user :

Hi there, I took these shots, and more besides flying into Bristol on a commercial flight.

The following are pictures attached with the email message
(http://www.phy.ntnu.edu.tw/ntnujava/pics/pic20060225a.png)
and
(http://www.phy.ntnu.edu.tw/ntnujava/pics/pic20060225b.png)

But I might say that the above two picture are not the same as the rainbow in the simulation.
I also saw it once when I am in an airplane,too. I can not recall it's name, now.

Title: Re: physics of Rainbow
Post by: gon on October 11, 2007, 03:39:38 pm
Mr. Fu-Kwun Hwang,

You are such a genius. My question is, how does double rainbow forms? I was once see a double rainbow when I am lying on the floor while fixing my jeep engine parts (http://www.aftermarketperformanceparts.com/jeep-engine-parts.html) saturday morning. And I was amazed because usual rainbows are single. How do we know about it? My friends are also amazed with it. Thanks in advance.

I have here an image of double rainbow:  http://www.photocentric.net/gallery/rainbows/RPrainbow2.jpg

-Ms. Gon.

Title: Re: physics of Rainbow
Post by: Fu-Kwun Hwang on October 11, 2007, 09:00:19 pm
I am not a genius. I learned it from standard textbook for physics. If you have enough resolution device, you even can see the third ranibow. But it will be very difficult, because the first two are pointing back to the direction of the sun, so you can see it while your back is face to the sun. (for the light coming from the sun, the intensity of the rainbow light  will be too weak compared to the light from the sun, so you would not be able to see it).

Intensity for the second rainbow is even weaker(2%) than the first one (about 5% of the intensity of sun light).
So normally, you might not notice it.

If you drag the horizontal red line with your mouse from the top and move it downward slowly.
Check out the angle for #3 ray (at the bottom you will find 3):
you will find the angle increase first, then at about 42 degree it become smaller again as you continue to drag the line down.
And the maximum angle is the angle you will find rainbow for red light (when the ray of incoming sun light is horizontal).

You will find #4 ray at the top. But when you drag the red line lower than the center of the water drop(big white circle)
the # 4 ray starts to point download. when it reach near 50 degree(also the maximum angle), that is the angle you will find the second rainbow.
Normally, when you watch the rainbow, the ray of the sun light is not horizontal.
If it is 15 degree higher, you need to substrate the 15 from 42 (or 50). So when the sun is too high, there is no way you will find rainbow in the ground (you might see rainbow from high enough mountain).
So you might be able to see the rainbow in the early morning or late in the afternoon.

I hope the above information will help.  I upload the picture for the rainbow, so more user can see the beautiful rainbow.
And I hope many of you can enjoy the fun of physics as I do.

Title: Re: physics of Rainbow
Post by: gon on October 12, 2007, 07:10:15 am
Wow... That was the double rainbow photo I have given you. It was really great to see. I can't really imagine that there is still a third rainbow.   :o  Wow ...... Thanks a lot. I gonna tell this to my friends and also ofcourse to meet you Mr. Fu-Kwun Hwang.  -*-

Title: Re: physics of Rainbow
Post by: nonymou on May 13, 2008, 11:33:16 pm
Dear Fu-Kwun,
Thank you for sharing this excellent work you have done.  This is a tremendous resource for understanding physics!  I am not a physicist, but I am working on a solar energy project and need to understand something about optics for concentrating sunlight with a lens, including the prismatic effect, as demonstrated by your rainbow applet.  I hope to be able to create an applet of the project I'm working on, building on the 'thick lens' and the 'rainbow'.  If I am successful, I'll post it for others to see.

Thanks again.

Title: Re: physics of Rainbow
Post by: Fu-Kwun Hwang on May 13, 2008, 11:38:52 pm
Good! I hope to be able to see your work soon. Good Luck!

Title: Re: physics of Rainbow
Post by: candacedwan on May 25, 2008, 12:24:11 pm
The effect of brightness inside the rainbow and darkness outside the rainbow intrigues me. Can you help me to understand this? Does the rainbow behave as a giant lens?

Title: Re: physics of Rainbow
Post by: Fu-Kwun Hwang on May 25, 2008, 11:55:30 pm
Did you noticed that there is a intensity vs angle diagram in the simulation?
Check out the diagram and think how it is related to your question.

Title: physics of Rainbow
Post by: Nick Lu on June 01, 2008, 01:30:02 am
Dear Admin. Fu-Kwun Hwang
I've already read your article about the rainbow, and I love it pretty much!! However, I still don't quite understand why the rainbow always looks like an arch as raindrops are everywhere, why do I only receive the refraction light spectrum from that arch not anywhere else? Besides, I've no idea how the hell this happened in these pictures as I tried to think about it but just had no idea... and in picture 721e67.jpg, the color of the cloud between the two rainbows is darker than the outside part, odes it have something to do with this phenomenon?
Thank you very much!

Title: Re: physics of Rainbow
Post by: Fu-Kwun Hwang on June 01, 2008, 11:51:20 am
We can drag the sun ray up and down and we will find ray #3 can be any angle.
If all the intensity of ray #3 are all equal, we would not be able to see rainbow.
But the intensity of ray #3 has a maximum value at particular angle (for red light near 42 degree).
The diagram in the simulation shows intensity of ray #3 and #4(secondary/outer and weaker rainbow) as function of angle.
There is a gap in which no ray will be refracted, so there is a region which will be darker in the space.

If we accept for horizontal sun ray, the view angle for red light will be near 42 degree (different angle for different color sun ray)
The light might enter our eye for us to see it. So all the light enter our eye with 42 degree is a cone.

If you move to a different position, you are viewing another rainbow. So the rainbow saw by different people are coming from sun ray refracted from different rain drop. (Your rainbow is for your eyes only!)

But 42 degree is for horizontal sun ray. If the sun is located at higher angle, then the angle you will find rainbow will be smaller. We will not be able to find rainbow at ground if the sun is above 42 degree (for example: at noon).
So we only find rainbow in the early morning or before sun set.

I hope the above explanation can help you understand more about rainbow.

Title: Re: physics of Rainbow
Post by: Fu-Kwun Hwang on June 26, 2008, 10:47:31 am
Quote
Dear Fu-Kwun Hwang,
I was looking for some good explanation about rainbow physics when I found this problem and still i cannot figure out an answer to this. I've been studying some optics this year and I've been told that the primary rainbow has always the red colour on its external part. Now, as seen in picture "Rainbow1.png" the red ray is refracted downward; so the observer should perceive it as the lowest one. Could you please give me the answer to this?

Different color of sun light refracted from the same water drop are refracted at slightly different angle. The distance between the person who saw the rainbow and the water drop are normally very large. So different color light refracted from the same water drop would not enter the same person's eye. The red light and the blue light saw by the same person are sun light refracted from different water drop. Please check out rainbowcolor.jpg

If you move to different position, the rainbow you saw was not the same one. And different person will see rainbow refracted from different water drops. Everyone saw his own rainbow. The rainbow you saw is for your eyes only.

Title: Re: physics of Rainbow
Post by: Fu-Kwun Hwang on April 02, 2009, 07:39:56 am
The following is a snap shot from a movie try to explain "physics of rainbow". However, the explaination is not correct. Can you find out what is wrong in the attached image?
Another incorrect statement in the movie : light enter the raindrop is "totally internal reflected" which is not true.

Title: Re: physics of Rainbow
Post by: Shamar712 on May 04, 2009, 03:02:12 am
Being new to this site and email was what I found first, I sent Mr. Hwang an email. The following is a copy of that email:

Mr. Hwang,

From my little understanding of rainbows, the following is not supposed to happen... but it did. In defense of myself I will say that I am an objectively led person with a background of finding problems missed by others. I am not given to fantasy and I assure you the following is true.

I walked through the end of a rainbow first noticed in my backyard at a distance of twenty yards. An eight foot cedar tree approx three feet behind the rainbow had a wavy appearance and its color had shaded towards grey from its normal green. Approximately ten feet from the ground the colors of the rainbow had faded and gave the apprearance of the air 'dancing'. Something like looking through a wine glass after swirling the wine and allowing it to settle down the sides of the glass.

As I walked through the thin bow the air turned clear on the far side and the cedar tree again took on its normal appearance. I had approached the bow at an angle of about 120 degrees (from approx twenty yards and the rainbow did not change positions) and walked thru it at an angle of about 90 degrees after observing for a moment. There was no sensation, other than awe, as I did so. I repeated the walk thru only twice as the bow dissipated.

I am not 'seeeeeing things'! How is this possible???

Note: Since writing this I have had the witness of others who state they also walked thru the end of a rainbow and found this: http://www.thenakedscientists.com/forum/index.php?topic=18551

Your help would be appreciated.
Shamar

Title: Re: physics of Rainbow
Post by: Fu-Kwun Hwang on May 04, 2009, 08:46:41 am
The rainbow in the above simulation is due to light enter raindrop/waterdrop , refracted twice and reflected once or twice.
The angle of the rainbow is nearly 42 degree.  And the rainbow is always at the same relative position no matter how you move. You can not pass it. Because see rainbow from different raindrop when you move.
However, there are several way to produce rainbow light pattern. e.g. light pass through a prism, the image in the URL you have provided, ...etc.

May I know what is the direction of the sun when you saw the rainbow? Is there any other strong light source around?

Title: Re: physics of Rainbow
Post by: Shamar712 on May 04, 2009, 09:19:54 am
<<<Dr. Hwang, "...May I know what is the direction of the sun when you saw the rainbow? Is there any other strong light source around?">>>

I do not remember the time of day, but think it was early afternoon. The attitude of the bow was approx NE to SW, me being on the SW end of the bow. The sun was shinning at my location and the rain clouds were just to the East of me.

There was no other light source.

Shamar

Title: Re: physics of Rainbow
Post by: lookang on May 04, 2009, 09:26:40 am
found in youtube is these great videos to complement the java applet.

The applet is great but i still cannot understand some parts of the physics of rainbow.

a quick view of this video provided me with a 3-D understanding of how the history and the current day understanding of rainbow is able to account for what we see.

The Scientific Explanation of Rainbows Part 1

enjoy!

Title: Re: physics of Rainbow
Post by: Shamar712 on May 04, 2009, 10:23:35 am
Your post is most appreciated, Lookang. I found it very interesting.

It does not seem to explain what I saw, however. I actually approached 'my bow' from outside the SW end of the bow at about 120 degrees, not in front of it. I do not recall for certain if I could see the air disturbance from the back side, but I think so - the air had a wavy appearance. I should have made my observation more precise, but... I was awe struck while trying to record what I was seeing.

I did not specifically note the arc of the rainbow as to its height, but as I remember the arc was more shallow than normally what I see.

The disturbance of the air really makes me wonder what? and why?, it is as though the air were ionized in some way. Is there a 'channel' of some sort generated in the air upon which to produce the bow itself???

Title: Re: physics of Rainbow
Post by: Shamar712 on May 06, 2009, 06:51:59 am
The rainbow in the above simulation is due to light enter raindrop/waterdrop , refracted twice and reflected once or twice.
The angle of the rainbow is nearly 42 degree.  And the rainbow is always at the same relative position no matter how you move. You can not pass it. Because see rainbow from different raindrop when you move.
However, there are several way to produce rainbow light pattern. e.g. light pass through a prism, the image in the URL you have provided, ...etc.

May I know what is the direction of the sun when you saw the rainbow? Is there any other strong light source around?

Mr. Hwang,
I do hope you have not dismissed my experience (or perhaps I did not understand your answer), some of the peripheral info may be in error, but I assure you the basic info is fact - I stood in that rainbow and passed through it twice. On the back side I did not see any other rainbow nor did I see a different bow at any time during the experience. That bow I did see was stationary the entire time.

Facts:
1. I stood in the bow and it was stationary
2. Standing in front of the bow, on the sun side, I could see the air 'slowly dancing' all the way to the ground. It was obvious, there was a rippling effect which distorted the air.
3. The cedar tree behind the bow had shaded towards grey when looking thru the bow and had a rippled effect.
4. The colors of the bow faded to clear from a few feet above my head (at least I could see no colors from ten feet down)

The following is a copy of an email I sent, in response to a request for additional info, to Kathy Coil @ noao.edu, there is more info:

Kathy,

I'll do the best I can, below, from memory, most of the info will only be
close. I have a rough understanding of  rainbow formation and the various
angles involved..., but, no understanding of how I am able to stand in a
rainbow. Is there any known explanatory geometry of a rainbow that would
allow for this???
.....I assure you, I stood in that rainbow, walked thru it and observed the
'wavy' effect in the air very closely (standing close I pondered what effect
it might have if I walked into it, so I first put my hand into the bow)...
as well as its effects on the cedar tree, as described, behind the bow.
.....The bow had faded its color from about ten feet off the ground and what
I was seeing was an obvious wavy effect in the air - no colors, just 'slow
dancing' air.

Time of day, not certain, but early afternoon in summer - sun had to be to
the NW. Weather: A light rain had passed from west to east, cloudy bright
and the sun was coming full - the remainder of the rain clouds were thin and
passing. It was not raining on me and the rain had passed by about a mile.
There were no other light sources, large trees or obstacles near, the
closest, a tree, at about forty yards to the NW and well below the angle of
the sun. (Sun angle? - I think it was in June near the equinox. Angle of the
arc to the sun (?), not sure, seems it was not straight on. It appeared to
me the bow was 90 degrees to the ground, or straight up. )

Stepping from a covered deck, going east, I saw the bow and that its end was
twenty yards from me to the SE. As I walked to the bow, it did not change
position, it remained stable.The bow ran from NE to SW, I was at the SW end
with the other end disappearing over a hill (width of the bow inknown - no
real reference) at perhaps a half mile. (I was in a valley approx a quarter
mile wide, on the west side of the valley.) Drawing a line from the base, to
the NW, of the bow perpendicular to the arc and calling it 90 degrees with
zero degrees being inside the arc, I approached the bow from 120 to 135
degrees and then stood directly in front of it within two feet observing the
interference in the air..

The base of the bow was narrow, about four feet wide, and the bow was very
thin from front to back, only a few inches. I stepped back and forth thru it
twice, slowly, before it disipated... and as I remember the sun was coming
full at that time.

Title: Re: physics of Rainbow
Post by: Fu-Kwun Hwang on May 06, 2009, 09:22:47 pm
I understand that you are talking about the experience you have (what you saw and what you feel).
The reason that I asked those question was I hope to be able to find more information.

If you saw "rainbow pattern" at the same location as you walk through. It means that there is a some kind of screen so that light can be reflected back to your eye.
We see object because light reflected from surface of the object and enter our eye (unless object is a light source).
Because the "rainbow pattern" you saw is not a light source, so it must be some kind of "screen" to be able to reflect light.
And I have not figure out why/how the rainbow pattern was formed from your information.
I hope someone else can provide a better explanation.
In case you see the same "rainbow" again, please remember to take some picture.
I believe it will help if we can see those picture!

Title: Re: physics of Rainbow
Post by: Shamar712 on May 07, 2009, 02:09:15 am
I understand that you are talking about the experience you have (what you saw and what you feel).
The reason that I asked those question was I hope to be able to find more information.

If you saw "rainbow pattern" at the same location as you walk through. It means that there is a some kind of screen so that light can be reflected back to your eye.
We see object because light reflected from surface of the object and enter our eye (unless object is a light source).
Because the "rainbow pattern" you saw is not a light source, so it must be some kind of "screen" to be able to reflect light.
And I have not figure out why/how the rainbow pattern was formed from your information.
I hope someone else can provide a better explanation.
In case you see the same "rainbow" again, please remember to take some picture.
I believe it will help if we can see those picture!

"...must be some kind of "screen" to be able to reflect light": My perception or thought at the time was that the air was inonized in some way and wondered if there were a 'channel' formed in the air - the ripple effect continued upward but was no longer visible as the colors of the bow became visible... not that it wasn't there. It was as though the colors of the bow were set upon the 'ionized' air. (???)

The following link, also hearsay, was something of interest I found:
http://jenniverse.com/impossible%20things%20rainbow.html

As circumstancial as the evidence is, it does appear there are stable rainbows that must have some sort of 'anchor' to the ground and to a location in the air... and perhaps over the entire course of the bow. I've often wondered what the other end of the rainbow looked like. (?)

Also, another witness to the same effect, I had asked if he noticed any anomaly in the air..... I did have to prompt him, however, he said after he thought about it there was also a 'ripple' effect in the air. He also stated that the air was not without color at the base as was my experience, rather there were colors to the ground as in the above link.

There is something 'strange' going on here - my curiosity is certainly piqued. My thought is there must be some sort of channel/"screen" or 'circuit' generated in the air as a foundation for the bow to permit such an experience to happen. (???)

Believe me, if such an occurrence happens again, and I am looking :o), I will find my camera in a hurry! You will have a video.

I appreciate the dialogue
Al

Title: Re: physics of Rainbow
Post by: Emosie on August 23, 2009, 09:37:10 am

re: rainbow halos and other

hiya i was hoping u could give me a bit of info about certain rainbows
i have a rainbow in my backyard its allways there no matter what time it is
(but u see it best if there is a bit of shade as when it is very bight its almost clear) if u spray the hose in my backyard
a rainbow appears but not just any rainbow one of these halo rainbows and its stands vertically not horizontally n close to the  ground
some times several more halo rainbows appear in side of it.
i thought that was  strange enough but Ive also noticed that there is one at night around 1am that circles the moon
any info is highly appreciated

Title: Re: physics of Rainbow
Post by: Fu-Kwun Hwang on August 23, 2009, 11:03:52 am
if you stand with your back to the sun so you are facing the same direction as the incoming sunlight, you need to look at an angle of 42.0 degrees to see the rainbow.

If the sun is located 42 drgree above the ground, the rainbow need to be formed with waterd drop below horizontal line where you stand.
We would not be able to see the rainbow at noon on the ground if the rainbow is form from sun light with water drop (cloud) in the sky. (Unless you are at a high place and looking down).

However, if the water drop is coming from spray the hose, you will be able to find rainbow any time (you stand with your back to the sun ---42 drgree is related to the direction of sun ray).

The pattern you saw at night circle the moon is not from the same way in the above simulation (air/water refraction-> reflection in water -> water/air refraction).
I think it is similar to rainbow from from a prism (due to air/water refraction->  water/air refraction).

Title: Re: physics of Rainbow
Post by: lookang on April 16, 2010, 10:40:49 am
(http://www.fisica.uniud.it/URDF/mptl14/img/testata1.gif)
was looking at http://www.fisica.uniud.it/URDF/mptl14/ftp/abstracts/T2_73_OP%20Abstract.pdf
Great Conference Multimedia in Physics Teaching and Learning MPTL 14!!

Hi Prof, you didn't submit full paper?  ;D it is not there

i reproduced the abstract here, so that people know your insights on physics education with simulation.

T2_73 NTNU VIRTUAL PHYSICS LABORATORY: JAVA SIMULATIONS IN PHYSICS
Fu-Kwun Hwang, Department of Physics, National Taiwan Normal University, Taipei, Taiwan
(hwang@phy.ntnu.edu.tw)
I have created many physics simulations for teaching purpose since 1996. The first simulation created is a
thin lens applet. The main targeted users are physics teachers who want to use java simulation to illustrate
physics concept in classroom ,or combine simulation with worksheet designed for students. I started to
create more complicate simulation, like "physics of rainbow". As a physicist, I found there are so many
physics involved with rainbow. So I tried to add as much information as I knew to the simulation. Yes. I felt
great when it was created because I also learned from the simulation that rainbow is highly polarized. It is
also a popular page. However, it is too complicated and too much information available so that most of the
students will not be able to really learn from it without help from teacher. It might be a good simulation for
talented students, but it is not a good simulation for most of the students who just learned physics for a
short time. And I do not think many teachers really use all the information available in the simulation.
Teacher want to have simulations with many options so s/he can use the same simulations for different
cases. However, student need simulations with the option they needed just for their problem or conquer
their concept barrier. For simulation developer: if you want to let people think that you are good in physics or good in simulation skill, go ahead and create more complicate simulations. But if we want to really help teachers or students, please design simulation just for their need. Do not try to give them too much unless
the purpose is not help students to understand the physics concept. Several hundreds of physics related
simulations are freely available at NTNU Virtual Physics Laboratory web site
(http://www.phy.ntnu.edu.tw/ntnujava/) The web site is a forum system so that user can ask questions
related to posted simulations. Login user will find "get file for offline use" button with "send to email
account" or "download directly" options. User can translate simulation web page and/or text symbols used
in the applet into local language format, so that it will be easier for their students. Enjoy it!

Title: Re: physics of Rainbow
Post by: koclup1580 on November 15, 2012, 12:28:25 pm
thank you ....

Title: Re: physics of Rainbow
Post by: anelinamartin on April 12, 2013, 12:27:24 pm
From my child hood i am wondering about rainbow. Then in 6th grade our teachers tell us little about it. But now i am completely understanding it. With the passage of time there will  definitely more research on that. Now imapct of childhood still prest on me that's why i like to ear rainbow colors jackets (http://www.gear4ride.com/Motrorcycle%20Leather%20Suits/) during my ride.

Title: Re: physics of Rainbow
Post by: anelinamartin on July 25, 2013, 12:13:25 pm
Its quiet helping. I love to see rainbow colors when cooking food and my -*-double oven-*- gone a help me.

Title: Re: physics of Rainbow
Post by: anelinamartin on August 21, 2013, 03:01:32 pm
Can you please share a collection of rainbow pictures with some effects of education.
-*-

Title: Re: physics of Rainbow
Post by: Fu-Kwun Hwang on August 27, 2013, 03:45:16 pm
(http://i3.mirror.co.uk/incoming/article2191100.ece/ALTERNATES/s615/Complete-rainbow-reflected-in-Conneticut-river-2191100.jpg)

Title: Re: physics of Rainbow
Post by: anelinamartin on April 25, 2014, 12:54:57 pm
Can you please share a collection of rainbow pictures with some effects of education.
-*-
Thank you for share. -*-

Title: Re: topic44
Post by: AntoniaCais on July 14, 2014, 11:26:59 pm
Quote from:  link=topic=44.msg277#msg277 date=1075424990
Subject: I saw a Polarized Rainbow!
Date: Sat, 14 Mar 1998 01:18:24 -0800
From: Neal Rasmussen <nealras1@airmail.net>
To: hwang@phy03.phy.ntnu.edu.tw
I am, as far as I know, the first to see a "Polarized Rainbow"!
I think we should name this phenomona the "Rasmussen-Wang Rainbow". :-)
I am a tornado chaser for 20 years. About 4 years ago I was driving through a McDonald's drive thru.
As it was just after a pretty good storm, I had mys polarized yellow tinted flip-up sunglasses on.
Low and behold I almost dropped my cigarette into my lap.
There off in the east was a double rainbow!
Not the kind I've seen dozens of times where the second one is reveresed and much outside the primary,
but this was immediatly INSIDE the primary!
Gaping with my mouth open and people behind me honking,
I flipped my flip-ups up and the second inner one went away!
I must have sat there for 2 minutes flipping my sunglasses.
The colors were NOT reversed and it looked like one continuous double wide rainbow,
with two complete sets of colors.
I ruled out that the flip-ups where giving double vision as I looked at lights the next day,
streetlights headlights, etc. and no doubles!
Can this possibly be? Could a source of polarized light be at a different angle,
perhaps the sun shining through a cirrus cloud or noctelucent (sp).
Neal Rasmussen nealras1@airmail.net
Really never heard about polarised rainbow.. I will try to gather some more details and share it out soon..