The seven types of radiation are radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. These make up the electromagnetic spectrum, arranged from lowest energy and longest wavelength (radio waves) to highest energy and shortest wavelength (gamma rays). All seven are forms of electromagnetic radiation, meaning they travel as waves of energy at the speed of light. What separates them is their wavelength and the amount of energy each photon carries.
Radio Waves
Radio waves sit at the low-energy end of the spectrum with the longest wavelengths, ranging from the length of a football field to larger than Earth itself. Despite their name, radio waves do far more than deliver music to your car stereo. Radio telescopes use them to observe planets, comets, gas clouds, stars, and entire galaxies. Wi-Fi, Bluetooth, and television broadcasts all rely on radio waves at various frequencies.
Microwaves
Microwaves occupy the higher-frequency end of the radio spectrum but are treated as their own category because of the distinct technologies built around them. A microwave oven uses waves about 12 centimeters long to force water and fat molecules in food to rotate rapidly, generating heat that cooks the food from the inside out.
Beyond your kitchen, microwaves are essential to satellite communication and navigation. GPS receivers use a microwave band called L-band, which can penetrate forest canopies to pinpoint your location. Weather satellites beam microwaves through storm clouds to map rainfall patterns underneath, and radar altimeters on ocean-monitoring satellites measure sea surface height by timing microwave pulses bounced off the water. In 1965, two scientists at Bell Labs accidentally detected faint microwave background noise with a specialized antenna, a discovery that turned out to be the afterglow of the Big Bang.
Infrared Radiation
Infrared radiation is the heat you feel radiating from a fire, a warm sidewalk, or another person’s body. It sits just below visible light on the spectrum, with wavelengths longer than what your eyes can detect. Scientists divide it into three subcategories: near-infrared, mid-infrared, and far-infrared. A TV remote control, for example, uses near-infrared energy at a wavelength around 940 nanometers to send signals to your television.
The thermal infrared band, roughly 8 to 15 micrometers, is especially useful for Earth scientists studying heat radiating from the planet’s surface. Night vision goggles work by picking up infrared light emitted by warm objects, which is why people and animals glow brightly in those images even in total darkness.
Visible Light
Visible light is the only part of the electromagnetic spectrum your eyes can detect, spanning wavelengths from about 380 to 700 nanometers. That narrow band contains every color you see. Violet sits at the short-wavelength end (around 380 nm), and red sits at the long-wavelength end (around 700 nm), with blue, green, yellow, and orange falling in between. White light from the sun is actually a blend of all these wavelengths, which is why a prism can split it into a rainbow.
Ultraviolet Radiation
Ultraviolet (UV) radiation carries more energy than visible light, covering wavelengths from 100 to 400 nanometers. The World Health Organization divides UV into three bands based on wavelength and biological effect.
- UVA (315 to 400 nm) accounts for about 95% of the UV radiation reaching Earth’s surface. It penetrates deep into the skin, causes immediate tanning, and contributes to skin aging and wrinkles. Recent evidence suggests it also plays a role in skin cancer development.
- UVB (280 to 315 nm) is more biologically active but only penetrates the outer skin layers. It causes delayed tanning, sunburn, accelerated skin aging, and significantly increases skin cancer risk. Most solar UVB is filtered by the atmosphere.
- UVC (100 to 280 nm) is the most damaging type, but the atmosphere filters it completely. It never reaches Earth’s surface under normal conditions, though artificial UVC lamps are used for sterilization.
X-Rays
X-rays have wavelengths ranging from about 0.01 to 10 nanometers, corresponding to energies between roughly 100 and 100,000 electron volts. That’s enough energy to pass through soft tissue but not through dense materials like bone or metal, which is why they’re so useful in medicine. Dentists use X-rays to image teeth, doctors use them to check for broken bones, and mammography uses lower-energy X-rays to improve contrast in soft tissue. Airport security scanners rely on the same principle to see through luggage.
X-rays also cross an important biological threshold. Along with gamma rays, they are classified as ionizing radiation, meaning their photons carry enough energy to knock electrons off atoms in your body and potentially damage DNA. Non-ionizing radiation (everything from UV on down through radio waves) generally lacks the energy to do this, though UV can still cause DNA damage through other mechanisms.
Gamma Rays
Gamma rays have the shortest wavelengths and the highest energy of anything on the electromagnetic spectrum. In space, they’re produced by the most extreme objects and events: neutron stars, pulsars, supernova explosions, and regions around black holes. On Earth, they come from nuclear explosions, lightning, and the steady, quieter process of radioactive decay.
Because of their extreme energy, gamma rays can pass completely through the human body. Stopping them requires several inches of lead or a few feet of concrete. In medicine, doctors use gamma-ray imaging to see inside the body, and targeted gamma radiation is used in certain cancer treatments to destroy tumors.
Ionizing vs. Non-Ionizing Radiation
One of the most practical ways to think about these seven types is where they fall on the ionizing divide. Radio waves, microwaves, infrared, and visible light are all non-ionizing. Their photons don’t carry enough energy to strip electrons from atoms in your cells. Ultraviolet sits in a gray zone: UVA and UVB aren’t traditionally classified as ionizing, but they still damage skin cells and DNA through chemical reactions. X-rays and gamma rays are firmly ionizing, with photon energies above 10 electron volts.
For context on safety limits, U.S. regulations set the annual public exposure limit from licensed nuclear operations at 1 millisievert per year, excluding natural background radiation and medical procedures. Background radiation from natural sources (radon in the ground, cosmic rays from space, trace radioactive elements in food) typically adds another 2 to 3 millisieverts per year for most people. Medical imaging adds a variable amount on top of that.
Particle Radiation vs. Electromagnetic Radiation
When people search for “types of radiation,” they sometimes expect to find particle radiation alongside the electromagnetic spectrum. These are fundamentally different. The seven types above are all waves of pure energy with no mass. Particle radiation, by contrast, involves actual subatomic particles with mass and (usually) charge flying through space.
The most common forms of particle radiation are alpha particles, beta particles, and neutrons. Alpha particles are heavy clusters of two protons and two neutrons. They’re very energetic but burn through that energy quickly, traveling only a few centimeters in air. They can’t even penetrate the outer layer of your skin. Beta particles are much smaller, fast-moving electrons emitted during radioactive decay. They travel farther than alpha particles but can still be stopped by a layer of clothing or a thin sheet of aluminum. Neutrons, having no electrical charge, interact with matter differently and can penetrate much deeper.
Cosmic rays are another form of particle radiation. These are fully ionized atoms, mostly protons, that stream through the solar system with energies ranging from about a million to a billion billion electron volts. When they hit Earth’s atmosphere, they create cascades of secondary particles: gamma rays, electrons, and muons that rain down to the surface. Your exposure to cosmic rays increases with altitude, which is why airline crews receive slightly higher annual radiation doses than people who stay near sea level.