What Are The Colors of the Rainbow? When you look at a rainbow in the sky, all the colors can seem to blend together, but there are seven distinct hues that form the arc.

In order, these are red, orange, yellow, green blue, indigo, and violet (in grade school, you may recall these colors in the acronym ROY G BIV). These colors combine to form all the other colors which we can see with our eyes, though they only form a small part of the electromagnetic spectrum.

Interested in learning more about light and how it works? Read on to discover some interesting facts about the electromagnetic spectrum, visible light, and more.

Bonus Facts to Arouse Your Curiosity

1. Why is indigo even included in the visible spectrum? Many people forget about it altogether or find it non-intuitive, and that’s for a very specific reason. Scientifically, there may very well be no real significance to it, and it really is just blue combined with violet.

It is believed that the reason for its addition to the spectrum as a “significant” color may have something to do with its religious connotations. Back when Isaac Newton was studying light, religious opinions were pretty prominent, and the number 7 had a better reputation than the number 6. Putting in indigo made the visible spectrum 7 colors instead of 6. Indigo is also given special significance in Hindu metaphysical tradition, where it accounts for one of the 7 chakras in the human body.

2. Visible light only accounts for a tiny portion of the electromagnetic spectrum, which also includes other types of light which we cannot see with our eyes. This includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. The radio waves have the lowest frequency, and the gamma rays have the highest frequency.

Visible light is wedged right in the middle of the scale. What’s even more interesting is that you can actually compare the size of the wavelengths to distinct objects to get a feel for how long the waves are. Radio waves are about as long as skyscrapers, whereas gamma rays are about as long as atomic nuclei. Visible light like the ROY G BIV spectrum includes wavelengths roughly the size of protozoans.

3. The colors that we see are the reflections of different frequencies of light. White is what we see when a surface reflects back all the colors at once. When all the frequencies are absorbed, we get black. Black, in that sense, is not really a color at all, but merely the absence of color and light. If only blue wavelength light is reflected from a surface, it looks blue. If only red wavelength light is reflected from an object, it looks red, and so on.

4. Other organisms can see frequencies of light that we cannot. There are many insects which can see ultraviolet light. We can only see a visible light representation of other parts of the spectrum, for example, when looking on infrared or UV monitors which detect low or high frequency light/heat. So we really have no idea what is like to really be able to see these other types of light.

5. Why does light divide in a prism into the colors of the rainbow? The reason is the interference of the glass. The different wavelengths travel through the glass at different speeds, which causes them to disperse and separate when they emerge from the glass on the other end. Glass, water and air all can slow down the movement of light.

6. The light-distance between Earth and the Moon is approximately 1.255 seconds.

7. Most of those exciting photographs you see of deep space taken by the Hubbell Telescope aren’t actually pictures made using visible light. Obviously the picture you see is in the visible spectrum, but it is a visible-light representation of light that falls in other parts of the spectrum. Many of those photos are infrared photographs. In other words, if you traveled to see those distant nebulas and galaxies, the sight you beheld with your eyes would not match the photograph.

8. The shorter the wavelength of light, the higher the frequency of the energy. High-frequency light can cause damage. UV, X-rays, and gamma rays are forms of radiation and can be dangerous to human, animal, and plant life. The Earth’s atmosphere fortunately blocks harmful rays from the Sun, though imperfectly. You still need to wear a hat, sunglasses and suntan lotion if you want to protect yourself adequately on bright days.

Learning about the electromagnetic spectrum can be fascinating, because once you realize just how small a portion of the spectrum accounts for visible light, you realize just how much of the universe we never have a chance to directly observe

• unless you’re looking at a rainbow, that is.

Our instruments provide us with visible representations of this invisible universe, but we never get to experience it for ourselves. Next time you look around you, just imagine how much more complex the world is than the image which you perceive with your eyes!