The electromagnetic spectrum, or EM spectrum, is all around us. The light we use to see, the microwaves that allow us to use our cells phones, the radio waves used to broadcast music to our cars, and the gamma rays used to treat cancer, are all the same waves varying only by wavelength and frequency. The EM spectrum has far-reaching uses that have changed the way we live. However alongside this, they also come with some hazards. For example, Gamma rays have the most energy and can cause cancer, but there are plenty of other types of radiation that can harm humans. The activities in this guide will help students master the different types of radiation in the EM spectrum.

## Background Information on the EM Spectrum

The electromagnetic spectrum is a way of organizing the different types of EM radiation we find in the universe. It is a continuous spectrum, meaning where one part finishes, another starts with no gaps. The parts of the EM spectrum all have one thing in common: they all travel at the same speed in a vacuum. All the waves travel at 3 x 108m/s or 300,000,000 m/s. Each different part has a different use and dangers that are related to their wavelength and frequency. As the frequency increases (and the wavelength decreases), the energy of the waves increase. The frequency and wavelength of the waves are related using v=fλ, where v is the velocity measured in m/s, f is the frequency measured in Hertz, and λ is the wavelength measured in m.

### Mnemonic Device for the Types of Electromagnetic Radiation

Radio Waves have the longest wavelength, the lowest frequency, and the lowest energy. They also have no real dangers because their energy is so low. Radio waves are used for broadcasting and communication.

Microwaves have the second longest wavelength. They are most commonly known for their use in microwave ovens. Microwaves are also used in mobile phones allowing us to communicate with people all around the world. Microwaves can be dangerous. If you were to put a person in a microwave oven, it would heat the water molecules inside the body and cook the internal tissues.

Infrared is what we, as humans, feel as warmth or heat. It is used in thermal imaging and night vision technology. Infrared is also used in optical fiber communication. Too much infrared can cause burns to your skin.

Visible Light is the narrow range of EM radiation that we can see. White light is made up of 7 colors: red, orange, yellow, green, blue, indigo, violet. This light can be split into each color, or dispersed, using a prism. A good way to remember this is to think of the letters making a name - Roy G. Biv. Visible light has a range of uses, including optical telescopy and optical microscopy. There are no real dangers associated with it, but too much visible light can damage the eye.

Ultraviolet radiation causes skin to tan and is used in tanning beds. It is also used to check for counterfeit bills. UV can also be used to sterilize drinking water, as it can kill harmful microorganisms by disrupting their DNA. High exposure to UV can also lead to an increased risk of skin cancer, which is why physicians recommend that we wear sunscreen on sunny days.

X-rays are commonly used for imaging in medicine and security. X-rays are very penetrating, which means they are difficult to stop; this allows them to be used for creating images of bones. They are only absorbed by dense material like bone and metal and can easily travel through soft tissue. They are also used in airport security. X-rays are ionizing and they can cause cancer.

Gamma rays are the highest energy EM waves. They have the shortest wavelength and the highest frequency. They are extremely ionizing and penetrating. They can be very hazardous to human health and are linked to the development of cancer. However, they can also be used to treat cancer. Gamma rays damage cells, and when cancerous cells are exposed to gamma radiation, they are damaged and can be killed. This can help stop the spread of cancer.

### Additional EM Spectrum Activity Ideas

1. Have your students make a storyboard to show what the world would be like without microwaves.
2. Get your students make a safety poster for medical professionals working in a hospital. How can they keep themselves safe from some of the harmful EM waves that are used in hospitals?
3. Have students create their own mnemonic devices for remembering the order to the EM spectrum (or the colors of light) and make a visualization to help them remember it.