Featured Research

from universities, journals, and other organizations

Triple rainbows exist, photo evidence shows

Date:
October 6, 2011
Source:
Optical Society of America
Summary:
Single rainbows are inspiring, double rainbows are rare, but tertiary rainbows have been elusive until a meteorologist provided guidelines that showed how to find them. Few people have ever claimed to see three rainbows arcing through the sky at once. In fact, scientific reports of these tertiary rainbows were so rare that until now many scientists believed sightings were as fanciful as Leprechaun's gold at a rainbow's end. These legendary optical rarities have finally been confirmed, thanks to photographic perseverance and a new meteorological model.

Top: (a) Original image of a third-order (tertiary) rainbow. The image was taken May 15, 2011, in Kampfelbach, Germany and is the first-ever picture of a tertiary rainbow. Two reference positions (A and B) for image orientation are indicated. (b) Processed version of image (a) after contrast expansion and unsharp masking, showing a rainbow-like pattern next to the image center, marked by the arrows. Bottom: The third-order (tertiary) rainbow (left), accompanied by the fourth-order (quaternary) rainbow (right). They appear on the sunward side of the sky, at approximately 40° and 45°, respectively, from the Sun. This is the first picture ever of a quaternary rainbow in nature and the second picture ever of a tertiary rainbow.
Credit: Top: Michael Grossmann/Applied Optics; Bottom: Michael Theusner/Applied Optics

Few people have ever claimed to see three rainbows arcing through the sky at once. In fact, scientific reports of these phenomena, called tertiary rainbows, were so rare -- only five in 250 years -- that until now many scientists believed sightings were as fanciful as Leprechaun's gold at a rainbow's end. These legendary optical rarities, caused by three reflections of each light ray within a raindrop, have finally been confirmed, thanks to photographic perseverance and a new meteorological model that provides the scientific underpinnings to find them.

The work is described in a series of papers in a special issue published this week in the Optical Society's (OSA) journalApplied Optics.

In addition to the confirmed photo of a tertiary rainbow, the optical treasure hunt went one step further, as revealed in another photo that shows the shimmering trace of a fourth (quaternary) rainbow.

Raymond Lee, a professor of meteorology at the U.S. Naval Academy, did not snap those pictures, but he did make them possible. One year ago, Lee predicted how tertiary rainbows might appear and challenged rainbow chasers to find them.

Although staggeringly rare, tertiary and quaternary rainbows are natural products of the combination of refraction, dispersion, and reflection inside raindrops. These are the same processes that create all rainbows, yet they are taken to their most extreme to produce these higher order variants. Refraction is when sunlight bends as it moves from air into water and vice versa. (Such bending makes oars look bent when partially submerged.) Water droplets bend each of the colors in sunlight by a slightly different angle. This is called dispersion, and it separates the colors to create a rainbow.

Most of that multicolored light passes through the other side of the raindrop, but some is reflected. The raindrop's spherical curves concentrate those reflections at 138 degrees from the Sun. This concentrated light is bright enough to create a visible primary rainbow.

A double rainbow occurs because not all that light exits the raindrop. Some is reflected back into the raindrop and goes through the whole process again. Although this light is dimmer, sometimes it is bright enough to produce a secondary rainbow just outside the first.

A third series of reflections creates a tertiary rainbow. It is even dimmer than the secondary rainbow, and much harder to find because instead of forming away from the Sun, a tertiary rainbow forms around the Sun. To see it, observers have to look into the Sun's glare.

This may be why only five scientifically knowledgeable observers had described tertiary rainbows during the past 250 years.

Lee reviewed each description. He eliminated one questionable account and found common elements in the others. All described tertiary rainbows that appeared for a few seconds against a dark background of clouds about 40 degrees from a brightly shining sun.

Along with colleague Philip Laven, Lee used a mathematical model to predict what conditions might produce visible tertiaries. First, they needed dark thunderclouds and either a heavy downpour or a rainstorm with nearly uniformly sized droplets. Under these conditions, if the Sun broke through the clouds, it could project a tertiary rainbow against the dark clouds nearby. The contrasting colors would make the dim tertiary visible.

When Lee presented his findings at last year's International Conference on Atmospheric Optics, it sparked heated discussion. Some scientists insisted that past descriptions were wrong and that tertiaries were too dim to see in the Sun's glare.

One attendee, Elmar Schmidt, an astronomer at Germany's SRH University of Applied Sciences in Heidelberg and a rainbow chaser, took the guidelines as a challenge. He alerted likeminded amateurs. Since then, Michael Grossmann and Michael Theusner have snapped photos of tertiary rainbows. One photo even shows a quaternary rainbow, and both images, which underwent only minimal image processing to improve the contrast under these challenging photographic conditions, appear in the same Applied Optics special issue as Lee and Laven's paper.

The day Grossmann photographed the tertiary rainbow, he first recalled seeing a double rainbow. When the rain intensified, he knew he had to turn toward the Sun. "It is really exaggerated to say that I saw it, but there seemed to be something," he says. The pictures he snapped in the rain were the first to show a tertiary rainbow.

Of the noteworthy discovery, "it was as exciting as finding a new species," Lee says.


Story Source:

The above story is based on materials provided by Optical Society of America. Note: Materials may be edited for content and length.


Journal References:

  1. Raymond L. Lee, Jr., Philip Laven. Visibility of natural tertiary rainbows. Applied Optics, 2011; 50 (28): F152 DOI: 10.1364/AO.50.00F152
  2. Michael Groίmann, Elmar Schmidt, Alexander Hauίmann. Photographic evidence for the third-order rainbow. Applied Optics, 2011; 50 (28): F134 DOI: 10.1364/AO.50.00F134
  3. Michael Theusner. Photographic observation of a natural fourth-order rainbow. Applied Optics, 2011; 50 (28): F129 DOI: 10.1364/AO.50.00F129

Cite This Page:

Optical Society of America. "Triple rainbows exist, photo evidence shows." ScienceDaily. ScienceDaily, 6 October 2011. <www.sciencedaily.com/releases/2011/10/111005111001.htm>.
Optical Society of America. (2011, October 6). Triple rainbows exist, photo evidence shows. ScienceDaily. Retrieved August 2, 2014 from www.sciencedaily.com/releases/2011/10/111005111001.htm
Optical Society of America. "Triple rainbows exist, photo evidence shows." ScienceDaily. www.sciencedaily.com/releases/2011/10/111005111001.htm (accessed August 2, 2014).

Share This




More Matter & Energy News

Saturday, August 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Tesla, Panasonic Ink Deal To Make Huge Battery 'Gigafactory'

Tesla, Panasonic Ink Deal To Make Huge Battery 'Gigafactory'

Newsy (July 31, 2014) — The deal will help build a massive battery factory that Tesla says will produce 500,000 lithium batteries by 2020. Video provided by Newsy
Powered by NewsLook.com
Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) — British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
7 Ways to Use Toothpaste: Howdini Hacks

7 Ways to Use Toothpaste: Howdini Hacks

Howdini (July 30, 2014) — Fresh breath and clean teeth are great, but have you ever thought, "my toothpaste could be doing more". Well, it can! Lots of things! Howdini has 7 new uses for this household staple. Video provided by Howdini
Powered by NewsLook.com
Smoked: 2015 Ducati Diavel Vs 2014 Chevy Corvette Stingray Drag Race

Smoked: 2015 Ducati Diavel Vs 2014 Chevy Corvette Stingray Drag Race

Cycle World (July 30, 2014) — The Bonnier Motorcycle Group presents Smoked; a three part video series. In this episode the 2015 Ducati Diavel takes on the 2014 Chevy Corvette Stingray Video provided by Cycle World
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins