Electromagnetic radiation


Light is a type of electromagnetic radiation. The visible light that humans can see is a small part of the electromagnetic radiation, and other types include radio waves, microwaves, infrared rays, ultraviolet rays, X-rays, and gamma rays. The types of electromagnetic waves are divided by frequency, which determines how they affect matter.


You may have heard that the sun emits radio waves, X-rays, gamma rays, etc. "in addition" to visible light, but actually they are all the same thing, and the visible light just appears special because our eyes react only to a certain range of frequency.


Please take a look at this page for the frequencies and colors of visible light.


Colors and Numbers 色と数値


Waves and Particles


Electromagnetic waves have properties as both particles and waves.


For example, electromagnetic waves are diffractive, meaning that they can go around behind obstacles just like waves on the surface of water. Thanks to diffraction we can watch TV or use cellular phones even when there is an obstacle between the antenna and the devices.