You're watching Freeschool! Light! It's all around us. But what is it? Where does it come from? And what does light have to do with color? Light is a kind of energy that travels in waves. It is made when matter is heated up or gains energy. Excess energy is released, in part, as light. This energy is called electromagnetic radiation. When we talk about light, we usually mean visible light, which is the light that we can see with our eyes, but there are more types of electromagnetic radiation that are invisible to us, including radio waves, microwaves, x-rays, and gamma rays. Scientists can detect and measure invisible radiation with special tools. Together with visible light, all these types of radiation are called the electromagnetic spectrum. All electromagnetic radiation travels in waves, but different types have different wavelengths. The wavelength of electromagnetic radiation or light is connected to how much energy it has. Light with a longer wavelength, like radio waves, has less energy, while light with a shorter wavelength, like gamma rays, has more energy. Visible light makes up only a tiny part of the electromagnetic spectrum, but it includes every color we can see. The most important source of light here on Earth is the Sun. We call ordinary sunlight white light, but it actually includes all the colors of visible light. These colors can be revealed when white light goes through a prism. When light passes through a prism or something like it, it slows down a little bit and bends. Some parts of the light slow more than others, and the light spreads out into the colors of the spectrum. If you want to see all of the colors in the visible light spectrum, look no further than a rainbow! Rainbows are made when water droplets in the air bend sunlight much like a prism. Usually when we talk about a rainbow, we say it is made of seven colors - red, orange, yellow, green, blue, indigo and violet. Each color has a different wavelength. Red has the longest wavelength in the spectrum of visible light, and violet has the shortest wavelength. All the other colors have wavelengths in between the two. The colors of a rainbow are always in the same order, because the colors are arranged according to their wavelengths! Red is always on the outside, because red has the longest wavelength - and violet is always on the inside, because violet has the shortest wavelength. Electromagnetic radiation with a wavelength outside the visible light spectrum is invisible to our eyes. Light with a longer wavelength than the reddest red our eyes can see is called infrared light. Light with a shorter wavelength than the most violet violet we can see is called ultraviolet. When we look at an object, we are actually seeing the light that is bouncing off of it. A green leaf looks green because the leaf absorbs all of the colors in the spectrum except for green, which it reflects. When the green light enters our eyes, our brain tells us it looks green. Things that look white are reflecting almost all of the visible light shining on them, and things that look black are absorbing almost all of the visible light shining on them. Light, both visible and invisible, is all around us. It travels from its source as a wave, bringing energy with it. Without light, there would be no colors! Take a look at the world around you, and remember! Everything you can see is just different wavelengths of reflected light. Goodbye till next time!