Human Vision Only Detects a Sliver of the EM Spectrum

Superfact 94: Light is electromagnetic radiation. The electromagnetic spectrum we deal with goes from long wave radiation at a frequency of 0.3 Giga Hertz to gamma rays at 30,000,000,000 Giga Hertz, and far beyond. Light that is visible to humans goes from around 428,000 Giga Hertz to 750,000 Giga Hertz. This is a very thin sliver in the electromagnetic spectrum. In addition, many animals can see beyond the spectrum visible to humans.

Esther’s writing prompt: April 8 : Vision

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If you consider wavelength instead of frequency, the electromagnetic spectrum goes from gamma rays at a wavelength of 0.00000000001 meters to long waves at a wavelength of 1,000 meters. Visible light has a wavelength of 0.0000004 meters to 0.0000007 meters. Again, human vision corresponds to only a thin sliver of the electromagnetic spectrum.

The picture shows the spectrum visible to humans as a horizontal bar at the top. This spectrum is superimposed on a wider spectrum below as a thin rainbow colored strip. The wider spectrum is also placed horizontally and goes from gamma rays to radio waves.
The visible color spectrum. Sunlight wavelength and increasing frequency vector infographic illustration. Visible spectrum color range. Rainbow electromagnetic waves. Educational physics line. Shutterstock Asset id: 1933622132 by Shutterstock Asset id: 1933622132 WinWin artlab.
The electromagnetic spectrum is vertical and goes from long waves at the bottom to gamma rays at the top. The spectrum visible to humans is a thin sliver in the middle.
The spectrum visible to humans highlighted on a spectrum going from long waves to gamma rays. Original:  Penubag Vector:  Victor Blacus, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0&gt;, via Wikimedia Commons

It should be noted that the spectra above go from long waves to gamma rays because that’s the range of the spectra we typically deal with. However, the electromagnetic spectrum continues far beyond that.

I consider “Human Vision Only Detects a Sliver of the EM Spectrum” a super fact because it is a well-known fact among those who have studied physics, and it is an important fact, and yet I believe it is a surprise to many.

The Spectrum Visible to Animals

A lot of animals can see beyond the spectrum visible to humans. For example, animals that can see UV light including reindeer, scorpions, butterflies, bees, salmon, hedgehogs, many birds, amphibians, and reptiles. Humans cannot see UV light. You can read about various animals that can see UV light here, here, and here.

It appears that dogs and cats can see UV light as well. The color vision of dogs is in general poor, at least on the red side of the visible spectrum. However, dog vision includes UV light that we cannot see.

There are two colorful horizontal bars in the picture representing how the spectrum appears to people and dogs. The top bar depicts human’s view, and the bottom one is dog’s view. The human’s view is more colorful, but the dog’s view extends into UV light on the left.
Picture is from psychology today.

Many animals can also see or detect infrared radiation. A famous example are snakes. However, many other animals can detect infrared radiation including mosquitos, beetles, and other insects, some bats, bullfrogs, wolves, foxes, and some fish.

My Other Responses to Esther’s Prompts

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Author: thomasstigwikman

My name is Thomas Wikman. I am a software/robotics engineer with a background in physics. I am currently retired. I took early retirement. I am a dog lover, and especially a Leonberger lover, a home brewer, craft beer enthusiast, I’m learning French, and I am an avid reader. I live in Dallas, Texas, but I am originally from Sweden. I am married to Claudia, and we have three children. I have two blogs. The first feature the crazy adventures of our Leonberger Le Bronco von der Löwenhöhle as well as information on Leonbergers. The second blog, superfactful, feature information and facts I think are very interesting. With this blog I would like to create a list of facts that are accepted as true among the experts of the field and yet disputed amongst the public or highly surprising. These facts are special and in lieu of a better word I call them super-facts.

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