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. | Human Vision Only Detects a Sliver of the EM Spectrum
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.

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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.

40 thoughts on “Human Vision Only Detects a Sliver of the EM Spectrum”

    1. I am sorry to hear that your dog is deaf. Your dog can see some of the UV light spectra (UV-A) but on the other end of the visible spectra his color vision is worse (see the right side of the picture). So unfortunately, he may not be able to see better than you. However, dogs have an awesome sense of smell. Our Pug’s hearing became worse towards the end of her life, but she didn’t go entirely deaf.

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      1. I’m glad that over the last 12 years we’ve combined hand signals (often inadvertently) with our verbal commands, so she knows most of what we are saying. But we also noticed that she now has to go check out things visually that she would normally have figured out by her hearing (like where we are in the house at any time).

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        1. I am sorry she is going deaf. However, it is a great idea to combine hand signals with verbal commands. I’ve read that hand signals are easier for dogs to understand and remember and in case they lose their hearing they still have that. It is something dog trainers recommend.

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    1. I agree, it is a fascinating fact. What I should maybe have mentioned is that dogs can hear ultra sound 45,000–65,000 Hz, significantly higher than the human limit of 20,000 Hz. And of course bats can hear ultra sound too. So there are other senses beyond vision that supercede human capability. Speaking about bats. Bats and dolphins have echolocation. Sharks have electroreception, migratory birds have magnetoreception, etc. I can sense more super facts coming up.

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  5. Another fascinating topic Thomas… our cat goes out at night and has a fully insulated house with heat pads. I go out last thing to leave him a snack and he was sitting on the ledge staring intently as something on the lawn by the bird table about 15 feet away. I walked over and it was not until I was nearly on top of it that I saw the hedgehog in the dark enjoying the messy bird’s throwaways on the lawn. The hedgehog got another treat with a banana.

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    1. Wow that is a fascinating story. In addition, to being able to see a wider part of the EM spectra, many animals can hear ultra sound, and have much better smell etc. It would be interesting to be able to experience that. I am so glad you gave the hedgehog a banana. Hedgehogs do not live (in the wild) in Texas, where I live, but I saw them all the time in Sweden where I grew up. Here in Texas we have a couple of other fun critters, opossum and armadillos.

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    1. Thank you so much Cindy, and you are right. In addition, to a seeing a wider vision spectra dogs can hear ultra sound 45,000–65,000 Hz, significantly higher than the human limit of 20,000 Hz, and not to mention their much better sense of smell. Other animals have keener senses as well, in different ways. Migratory birds can sense the magnetic field.

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  7. Interesting!

    I once saw a YT about sound frequency. Did a quick search, but couldn’t find it.

    It was a sound file, starting at the sub level of our low end, rising slowly, until it whistled past our upper range.

    I played it through the home theater system for the fam, starting with a bass rumbling. As it rose, their hands drifted to their ears and they gave me annoyed looks. The dogs looked uncomfortable, then uneasy.

    As it became higher, then piercing, shouting and hand waving replaced the looks, and the dogs ran around, barking and howling. I was not popular the rest of the day, but the kids still remember the day they learned about frequencies 😎

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    1. That is a very cool experiment that you did. I did not write about but dogs can hear ultra sound 45,000–65,000 Hz, significantly higher than the human limit of 20,000 Hz. Also children pick up on some ultra sounds.

      Then of course bats can hear ultra sound too. So beyond vision there are other senses that supercede human capability. Bats and dolphins have echolocation. Sharks have electroreception, migratory birds have magnetoreception, etc. (I think I can sense more super facts coming up).

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  8. This was a point made to me early in my astronomy education. Most of my career has been spent in that narrow, visible part of the spectrum, but I’ve also taken radio and IR data. Most of the infrared data we take from the ground is in the so-called near-IR (those infrared frequencies closest to visible light) because Earth’s atmosphere absorbs a lot of IR light.

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      1. That’s correct. Spacecraft can really help with IR astronomy. When I was in high school, the space telescope IRAS (Infrared Astronomy Satellite) was big news because of the discoveries it was making. This is also one of the reasons JWST is optimized to work in the infrared. In the history of astronomy, that’s one of the best and most effective infrared telescopes that’s been launched and we can learn a lot from it since so many objects emit infrared light.

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