The Electromagnetic Spectrum Revealed 1

Feel the sun’s rays Hear your favorite song Get an x-ray at the dentist Make popcorn in the microwave You are using ELECTROMAGNETIC ENERGY 2

What is the electromagnetic spectrum (EMS)? Waves of energy characterized by their wavelength, frequency, and energy emitted. Different kinds of radiation, which is just energy that travels and spreads out as it goes. 3

– visible light – radio waves – microwaves – infrared rays – ultraviolet rays – x-rays – gamma rays What does the electromagnetic spectrum (EMS) encompass? 4

These are the different types of radiation in the EMS. ↑ longest wavelength ↑ lowest frequency ↑ lowest energy ↓ shortest wavelength ↓ highest frequency ↓ highest energy 5

Wavelength and Frequency Wavelength = Physical size of wave Frequency = Number of waves in a given period 6

Wavelength & Frequency The shorter the wavelength… …the higher the frequency. 7

EMS Wavelength … from shortest to longest 8

Long wavelength…low frequency Short wavelength…high frequency 9

Energy (from highest to lowest) shorter wavelengths & higher frequency = more energy decreasing wavelength increasing increasing frequency decreasing increasing ENERGY decreasing 10

Approximate sizes of electromagnetic waves 11

This shows both the size of a wavelength and possible sources of the radiation. 12

Short descriptions of the types of radiation…. 13

Radio waves have the longest wavelength and the lowest frequency in the EMS. They emit the least energy. 14

Microwaves are shorter waves with more energy. We use them to cook food. 15

Infrared radiation makes our skin feel warm. We think of IR being heat. Visible light is the only part of the spectrum that our eyes can see. 16

Visible light is a very small part of the electromagnetic spectrum. 17

Colors of Visible Light (from least energy to most energy) RedOrangeYellowGreenBlueViolet Red  Orange  Yellow  Green  Blue  Violet Roy g bvRoy g bvRoy g bvRoy g bv 18

Ultra-violet rays from the sun can burn our skin. The ozone layer helps protect us from UV rays. 19

X-rays are high-energy radiation that can penetrate soft tissue. That is why doctors and dentists use x-rays to look at our bones and teeth. 20

Gamma rays have the shortest wavelength, the highest frequency, and radiate the most energy. Radioactive materials emit gamma rays. 21

Wavelength & Frequency In remote sensing, we detect and sample energy at different wavelengths and frequencies. These different frequencies tell us different things about the object being sensed. 22

Although our eyes can directly perceive only a small portion of the electromagnetic spectrum... …we can gather more information by using other portions of the EMS such as infrared. 23

This chart shows how well various frequencies penetrate the atmosphere. As expected, visible light penetrates the easiest. Visible Light 24

Infrared easily penetrates the atmosphere, as well. For this reason, infrared is used in creating remote sensing images. Infrared Notice that the infrared band is very broad. This allows a wide choice of remote sensing frequencies each of which is useful for a specific purpose. Visible Light 25

Energy that strikes the Earth’s surface can be… …or all three. ENERGY Reflected Absorbed Transmitted 26

Energy Interaction Different surfaces also reflect energy differently. 27

For Help: AMSTI-GLOBEThe GLOBE Program Lynn Vaughan AMSTI-GLOBE Resource Specialist Robin NelsonJerry CobbsAMSTI-GLOBE AdministratorTechnology Specialist 28