Pocket Genius Science: Energy and forces – The EM spectrum

Facts At Your Fingertips: Energy and forces – The EM spectrum

Electromagnetic (EM) radiation is a form of energy that travels in waves at a speed of 186,000 miles (300,000 km) per second, which is the fastest speed in the universe.

Different kinds of radiation make up the EM spectrum. All types of radiation except visible light are invisible.

The spectrum

The EM spectrum is made up of seven major types of radiation, which vary in the length of their waves. The shorter the radiation’s wavelength, the higher its energy.

The longest waves can be many miles long, while the shortest are shorter than a single atom.

Radio waves have the longest wavelength. Radio and TV broadcasts and Wi-Fi use radio waves.

Microwaves are used to heat food. They are also used by cell phones.

Low-energy waves Hot objects, including mammals, give off invisible rays of heat called infrared (IR) waves.

X-rays have enough energy to pass through many materials. They are used to scan the contents of bags at security checks.

Visible light includes all the colors of the rainbow.

Sunlight contains ultraviolet (UV) rays. Goggles, sunglasses, and sun screen protect the eyes and skin from UV rays, which can be harmful.

Gamma rays have the highest energy of all. Observatories measure gamma rays emitted by very hot stars and other bodies in space.


The remains of dying stars, such as the Crab Nebula, give out large quantities of radiation, including powerful bursts of gamma rays.

Although this nebula is 30 million miles (50 million km) wide, it can now only be seen through a telescope. When it first formed, it could be seen with the naked eye.

The explosion of the star that formed the Crab Nebula in 1054 CE was that it was visible from Earth, 39,000 trillion miles (62,000 trillion km) away