The Electromagnetic Spectrum Have participants complete the Wavelength and Frequency worksheet prior to viewing this slideshow. They will come back to this sheet at Slide 6.

Waves… a review Most waves are either longitudinal or transverse. Sound waves are longitudinal. But all electromagnetic waves are transverse…

What is the electromagnetic spectrum (EMS)? Different kinds of radiation, which is just energy that travels and spreads out as it goes. Produced by the movement of electrically charged particles Can travel in a “vacuum” (they do NOT need a medium

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

These are the different types of radiation in the EMS. longest wavelength lowest frequency lowest energy shortest wavelength highest frequency highest energy Sometimes the electromagnetic spectrum is depicted starting from shortest wavelength to longest, starting with gamma rays. Have participants complete the Wavelength and Frequency worksheet before moving to next slide.

Wavelength and Frequency Wavelength = Physical size of wave Have participants look at their Wavelength and Frequency worksheet that was completed prior to the powerpoint. The symbol for wavelength is lambda (λ). It shows the distance from wave crest to wave crest. Which of these wavelengths is the longest? The shortest? Ask participants : “How did you determine the wavelength for each wave?” Have them share their measurements. Frequency = Number of waves in a given period

Wavelength & Frequency The shorter the wavelength… Ask participants: “How did you determine frequency?” Be certain they understand that frequency can be measured, not simply observed, by counting the number of waves that occur during a given interval (iiii. shows 1 complete wave, i. shows 2 waves, and ii. shows 4 waves). If the horizontal line represents one second of time on each graph, you can see that the shorter the wavelength, the more of them will fit into that one-second span. Thus the shorter the wavelength, the higher the frequency. Which has the highest frequency? (ii) The lowest? (iii) You may also ask: Which line has the shortest wavelength? (ii) Which line has the longest wavelength? (iii) …the higher the frequency.

EMS Wavelength …from shortest to longest Notice how long the radio waves are: 10 to the third cm (103cm) or longer (which is 10 meters or so) and how short the gamma rays are: 10 to the minus 11th cm (10-11cm) (or 0.00000000001 cm)! Looking at the Wavelength and Frequency worksheet, ask “Which illustration is most like a gamma ray? “ (ii) “Which is most like a radio wave?” (iii)

Long wavelength…low frequency Short wavelength…high frequency Long wavelength…low frequency

Energy (from highest to lowest) shorter wavelengths & higher frequency = more energy Which has the least energy? (radio waves) Which has the most energy? (gamma rays) At the bottom of the graphic, note the change in Energy Frequency Wavelength Finishing the Wavelength and Frequency worksheet: Ask participants “Which wave has the most energy and on what did you base your choice?” (ii) decreasing wavelength increasing increasing frequency decreasing increasing ENERGY decreasing

Approximate sizes of electromagnetic waves NOTE this illustration is backwards from illustrations on the 3 previous slides (which showed radio waves on the right and gamma ray waves on the left) - that is, this diagram shows, left to right, decreasing wavelength (increasing frequency & energy).

This shows both the size of a wavelength and possible sources of the radiation. (This illustration has the same orientation as the previous slide.) What is a possible source of infrared radiation? (people or light bulb)

Parts of Electromagnetic Spectrum Try: Rabbits
Meet
In
Very
Unusual
eXpensive
Gardens  meaning: Radio
Microwaves
Infra-Red
Visible light
Ultra-violet
X-rays
Gamma rays

Radio waves - Have the longest wavelength and the lowest frequency in the EMS. - They emit the least energy. Uses: *TV broadcasting *AM and FM broadcast radio *Avalanche beacons *Heart rate monitors *Cell phone signals RADIO WAVES

Microwaves are shorter waves with more energy. Uses:. Microwave ovens Microwaves are shorter waves with more energy. Uses: * Microwave ovens * Bluetooth headsets * Broadband Wireless Internet * Radar * GPS Microwaves fall between Radio waves and Infrared Waves.

Infrared radiation - makes our skin feel warm. Uses: Infrared radiation - makes our skin feel warm. Uses: * Night vision goggles * Remote controls * Heat-seeking missiles Visible light - is the only part of the spectrum that our eyes can see.

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

Colors of Visible Light (from least energy to most energy) ROY G. BIV Why do you think the visible light spectrum is usually written from red to violet instead of violet to red? (Hard to say VBG Y. OR???? Notice that “indigo” is now left out– it went the way of Pluto.)  Red  Orange  Yellow  Green  Blue  Indigo Violet Lowest Highest Frequency Frequency

Ultra-violet rays - Rays from the sun can burn our skin Ultra-violet rays - Rays from the sun can burn our skin. The ozone layer helps protect us from UV rays. Uses: * Black lights * Sterilizing medical equipment * Water disinfection * Security images on money Why might ozone depletion cause a problem? (More UV rays, more damaging radiation, more skin cancers, crop damage, etc.)

Ultra-Violet Rays UVA UVB and UVC Energy Highest of UV waves Lower than UVA Health risks Extremely low risk for DNA damage Can destroy Vitamin A in skin Can cause DNA damage, leading to skin cancer Responsible for sunburn

X-rays - are high-energy radiation that can penetrate soft tissue X-rays - are high-energy radiation that can penetrate soft tissue. Uses: * Medical imaging * Airport security * Inspecting industrial welds

Gamma rays - have the shortest wavelength, the highest frequency, and radiate the most energy. Radioactive materials emit gamma rays as do stars. Uses – * Food irradiation (Controlling Spoilage) * Cancer treatment (Can cause mutations in cells) * Sterilizing medical equipment

Wavelength & Frequency In remote sensing, we sense and sample energy at different wavelengths and frequencies. These different frequencies tell us different things about the object being sensed. Remember, ALL types of electromagnetic energy (light, radio waves, x-rays, etc) are categorized by wavelength and frequency.

…we can gather more information by using other portions of the EMS 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

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

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 Infrared

Energy that strikes the Earth’s surface can be… Reflected Absorbed Transmitted The interaction of this ENERGY with the Earth’s surface (trees, sand, parking lot, water, etc.) is the basis for taking infrared measurements to “Ground Truth” remote images. …or all three.

Different surfaces also reflect energy differently. Energy Interaction You’ll see this when you do your infrared mapping. Different surfaces also reflect energy differently.