Can you ‘create’ new rainbow colors?

How a new process for creating rainbows can speed up your Internet connection

MANILA, Philippines – A story Rappler published about how scientists at University of California in Santa Barbara (UCSB) ‘created’ 11 new rainbow colors has generated much commentary and criticism online.

Issues raised were:

  • Is it even appropriate to discuss the UCSB findings in the context of the rainbow, since the scientists themselves didn’t say rainbow in their press release?
  • Were the colors really new? It is possible to ‘create’ or ‘add’ new colors to the rainbow?
  • Is it correct to say that kids should now forget about ROY G BIV, everyone’s favorite memory guide to the colors of the rainbow?

 

The confusion came from a portion of a press release from the UCSB which said that an experiment conducted by a team of physicists at the university resulted in the creation of “multiple frequencies of light” simultaneously.

ROY G. BIV stays

The scientists themselves did not say that the colors were new rainbow colors. What the press release said was that, of the light frequencies created as a result of the experiment, 11 were new. “Each frequency,” Mark Sherwin, one of the physicists said in the release, “corresponds to a different color.”

Technology site Gizmodo initially ran the story with the headline, “Physicists add 11 colors to the rainbow by tearing apart atoms.”

Rappler also ran the same story and suggested that kids may need to forget about ROY G BIV, which stands for red, orange, yellow, green, blue, indigo and violet.

To clarify the issue, Rappler talked to scientists from the National Institute of Physics at the University of the Philippines.

In summary, they told us that it is wrong to tell kids to forget about ROY G BIV. But they added it is not wrong to discuss the findings of the experiment of the UCSB scientists in the context of the rainbow.

Visible spectrum

“It is just semantics,” as far as optical physicist Percival Almoro is concerned. “You need to discuss the subject using something people are familiar with, something they understand. If you talk of light as having different frequencies or wavelengths, mahirap maintindihan.”
 
In contrast, he said, everybody is familiar with the rainbow.

In the natural environment, rainbows occur when the sun shines through droplets of moisture, such as rain, in the Earth’s atmosphere. This is your conventional rainbow. But this is not the only time when the “rainbow effect” can be observed, the scientists said.

The same effect can be observed, Almoro said, when visible light is “dispersed or scattered upon incidence on a surface or medium.” Examples of this, he said, would be when light passes through a prism or an aquarium or shines through the grooves of a compact disc.

The rainbow colors, Almoro explained, is in fact the spectrum of visible light. When it passes through a surface, light is dispersed, “the components of what otherwise is white light become evident.”

Color range, not distinct bands

Kids are taught that the colors of the rainbow are red, orange, yellow, green, blue, indigo and violet, otherwise known as ROY G. BIV.  These are, in fact, merely the conventional rainbow colors, Giovani Tapang, another UP Diliman physicist specializing in optics told Rappler.

In truth, the scientists say, what we see as distinct bands of colors in the rainbow is actually a continuous spectrum. “The naked eye is unable to distinguish gradients,” Almoro expounds. “We can distinguish blue and red. You don’t see the distinctions in between.”

Can “new colors” be created?

Except for pink, all colors that we see are part of this spectrum of visible light.

If you think of the rainbow in those terms, then technically, it is not possible to create a new colors since everything is within the spectrum, Tapang says.

The constant challenge for optical physicists, according to Almoro, is to find ways to produce “exotic wave lengths”– or light at particular defined frequencies.

“This is pretty standard. We are also doing this at UP using different light sources,” he added.

The colors optical physicists produce in their experiments are technically still in the spectrum he says, “but our eyes cannot distinguish them when they are spread in a rainbow.”

The sequence of colors within the spectrum also remains constant. So in a sense, even when new “exotic wavelengths” within the spectrum are created, ROY G BIV will remain.

Light source and process: the Holy Grail

The ultimate purpose of producing these “exotic wavelengths” is for use in special applications that require them, Almoro said. Examples of these are biomedical applications such as UV lasers and IR or infrared lasers and visible lasers.

In the UCSB press release, Mark Sherwin, one of the physicists involved in the experiment, noted that it’s fairly routine to mix the lasers and get one or two new frequencies. “But to see all these different new frequencies, up to 11 in our experiment, is the exciting phenomenon.”

Tapang said these may not necessarily be new colors in the universe of colors known to man. A “new frequency” might correspond a new shade of blue, “but it is still blue.”

What is often new is that now you are able to identify a light source and the process through which distinct “exotic wavelengths” or “new frequencies” are produced.

“Light from sources are usually due to processes that emit certain definite frequencies,” Tapang, who specializes in optics, explained. “Some of these process are familiar such as burning (the blue flame of the LPG) or the red-orange neon signs.”

New way to produce a rainbow

The impressive thing that the UCSB team did, according to Tapang, was that “they can create several well defined frequencies at a time, something that has not yet been done.”

This is remarkable, he says, because the processes that create light usually make only certain frequencies (color) at a time. In way, Tapang said, what the team of scientists at the UCSB discovered was “a new way to create a rainbow.”

Not all light sources produce the entire range of wavelengths that we see in the rainbow, says Almoro. “In depends on the light source: for instance, the light bulb–because of the heating of filament in the light bulb–results in the emission of all the wavelengths in the visible spectrum.”

The scientists, the UCSB press release said, performed an experiment where they aimed high-and low-frequency laser beams at a semiconductor. In the process, they caused electrons to be ripped from their cores, accelerated, and then smashed back into the cores they left behind.

This recollision, according to the press release, produced multiple frequencies of light simultaneously.

Faster Internet

In terms of real-world applications, the electron-hole recolision phenomenon has the potential to significantly increase the speed of data transfer and communication processes, according to the UCSB scientists.

One possible application involves multiplexing–-the ability to send data down multiple channels–and another is high-speed modulation.

“Think of your cable Internet,” explained Ben Zaks, a UCSB doctoral student in physics and the paper’s lead author.

“The cable is a bundle of fiber optics, and you’re sending a beam with a wavelength that’s approximately 1.5 microns down the line. But within that beam there are a lot of frequencies separated by small gaps, like a fine-toothed comb. Information going one way moves on one frequency, and information going another way uses another frequency. You want to have a lot of frequencies available, but not too far from one another.”

The electron-hole recolision phenomenon does just that –– it creates light at new frequencies, with optimal separation between them. – Rappler.com