In this International Year of Light, it is particularly appropriate to review the historical concept of what is light and the controversies surrounding the extent of the visible spectrum. Today we ...

Classically, light can be thought of in two ways: either as a particle or a wave. But what is it really? Well, the ‘observer effect’ makes that question kind of difficult to answer. So before we get ...

What is blue light? “All the light we see is made up of different wavelengths of light,” says Vivienne Sinh Hau, MD, an ophthalmologist at Kaiser Permanente in Riverside, California. “Certain ...

Why is light affected by gravity if photons are massless? originally appeared on Quora: the place to gain and share knowledge, empowering people to learn from others and better understand the world.

Ultraviolet light is a type of electromagnetic radiation that makes black-light posters glow, and is responsible for summer tans — and sunburns. However, too much exposure to UV radiation is damaging ...

It’s in your physics textbook, go look. It says that you can either model light as an electromagnetic wave OR you can model light a stream of photons. You can’t use both models at the same time. It’s ...