Science

Living at Light Speed

Introduction to electromagnetic radiation

Our world runs and is connected [GB1] by electromagnetic energy that travels in waves at the speed of light. When you use GPS navigation for directions, play a video game using a remote controller, watch a sunset, get money from an ATM, or cook dinner in a microwave oven, you are using or sensing electromagnetic energy, or electromagnetic radiation.

Radiation is energy that moves in the form of particles or waves. Electromagnetic waves and are formed when an electric field couples with a magnetic field, and unlike sound waves, can travel through the vacuum of space.

The most familiar form of radiation is visible light. It consists of all the colors our eyes can see. Each color has a different frequency and wavelength creating a spectrum of colors - from reds and oranges, through blues and purples. So, whether you are enjoying a sunset or watching a movie, you are sensing electromagnetic energy.

Colors also have different energy depending on their wavelength. Colors with shorter wavelengths, like violet and purple, have a higher frequency and the more energy. Longer wavelengths, like red, have a lower frequency and less energy.

Visible light is just a small part of a larger electromagnetic spectrum with waves varying in length from long radio waves the height of a skyscraper, to very short gamma-rays smaller than the size of the nucleus of an atom.

Types of Electromagnetic Radiation

The benefits of harnessing this energy in our daily lives are hard to count. Sat radio, Sat tv, medical, visible, microwave oven, Bluetooth, WiFi, cordless phones, cell phones, radar, radio-controlled drones, and video controllers.

The amount of energy varies across the spectrum and is determined by wavelength and frequency. Wavelength is the distance between the crests of a wave. Frequency is the number of times a crest passes a point each second, usually measured in Hertz. Long wavelengths have a lower frequency and less energy than shorter waves. Ionizing radiation is a very high-energy form of electromagnetic radiation and includes the shortest wavelengths in the spectrum (ultraviolet waves, x-ray, and gamma rays).

Our exposure to radiation on the electromagnetic spectrum

Source: National Institute of Environmental Health Sciences

Short, waves like X-Rays, have a lot of high energy. They are so powerful, they can be harnessed by doctors to kill cancer cells. Very long waves, like radio waves, have the ability to pass through clouds and atmospheric interference making them good for satellite radio, GPS, and other wireless communication.

A sound wave is an example of a mechanical wave. Like waves in the ocean or ripples through a flag, mechanical waves require a medium to travel through. We can’t see sound waves because they travel through molecules in the air (like ocean waves travel through water). Sound cannot travel in outer space because there are no molecules to transmit through.

Electromagnetic waves are formed when an electric field couples with a magnetic field. These waves are unlike sound waves because they do not require a medium. Our main natural source of electromagnetic energy travels to us from the sun through space. Waves through the atmosphere, between antennas, and with satellites.

Harnessing the Spectrum for People

Benefits of ionizing and non-ionizing radiation

Radiation exists all around us, from both natural and artificial sources, and is in two forms: ionizing and non-ionizing radiation.

Electromagnetic Spectrum

Most of the radiation in the electromagnetic spectrum that we are exposed to is non-ionizing radiation.

Ionizing radiation has enough energy to knock electrons out of atoms causing the atom to become ionized and damage the structure of cells. A general term for high-energy particle beams and electromagnetic waves. Gamma Rays and X-rays are ionizing because they have enough energy to interact with and ionize atoms. This is helpful to doctors who want to target cancer cells with x-rays.

On Earth, we are constantly exposed to low levels of radiation. Cosmic radiation is a natural source of radiation produced by stars and our sun that includes high-energy charged particles, x-rays, and gamma rays. Other natural sources include terrestrial radiation from the decay of radioactive materials in the earth (e.g., radon) and some building materials (e.g., concrete, sandstone, brick) emit low levels of radiation.

Natural sources typically at low levels of ionizing radiation. This means that the usual amount of ionizing radiation from natural sources absorbed by our bodies (dose) is small.

[Difference between “radiation” and “radioactive”]

Non-ionizing radiation has less energy than ionizing radiation and does not remove electrons from atoms or molecules of materials that include air, water, and living tissue.

Energy with the longer wavelengths and lower energy in the spectrum – Visible light, microwaves, and radio waves – are non-ionizing. Meaning they don’t have enough energy to alter atoms and damage cells. However, exposure to large amounts of some non-ionizing radiation can be harmful. Our eyes are sensitive to the visible light region of the spectrum enabling us to see the world around us. But you wouldn’t want to look directly into a powerful light source like a spotlight or stadium lighting.

Location of RF communication on the spectrum.

Close exposure to large amounts of non-ionizing radiation can also cause heating. Energy in the microwave region of the spectrum, for example, have wavelengths about the size of molecules which can vibrate and cause the molecules to heat up. This is how microwave ovens work. Large amounts of microwave radiation vibrate water molecules which in turn heats your food.

[Heating and exposure guidelines]

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