the electromagnetic spectrum. most waves are either longitudinal or transverse. sound waves...
Post on 28-Dec-2015
Embed Size (px)
The Electromagnetic Spectrum
Most waves are either longitudinal or transverse.Sound waves are longitudinal.But all electromagnetic waves are transverseWaves a review
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 particlesCan travel in a vacuum (they do NOT need a medium
visible light radio waves microwaves infrared rays ultraviolet rays x-rays gamma raysWhat does theelectromagnetic spectrum (EMS) encompass?
These are the different types of radiation in the EMS. longest wavelength lowest frequency lowest energy shortest wavelength highest frequency highest energy
Wavelength and FrequencyWavelength = Physical size of waveFrequency = Number of waves in a given period
Wavelength & FrequencyThe shorter the wavelengththe higher the frequency.
EMS Wavelength from shortest to longest
Long wavelengthlow frequencyShort wavelengthhigh frequency
Energy (from highest to lowest)shorter wavelengths & higher frequency = more energydecreasing wavelength increasing
increasing frequency decreasing
increasing ENERGY decreasing
Approximate sizes of electromagnetic waves
This shows both the size of a wavelength and possible sources of the radiation.
Parts of Electromagnetic SpectrumTry:RabbitsMeetInVeryUnusualeXpensiveGardensmeaning:RadioMicrowavesInfra-RedVisible lightUltra-violetX-raysGamma 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
Microwaves are shorter waves with more energy.Uses:* Microwave ovens* Bluetooth headsets* Broadband Wireless Internet* Radar* GPS
Infrared radiation- makes our skin feel warm. Uses:* Night vision goggles* Remote controls* Heat-seeking missilesVisible light - is the only part ofthe 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)Red Orange Yellow Green Blue Indigo Violet Lowest Highest FrequencyFrequency ROY G. BIV
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
UVAUVB and UVC
EnergyHighest of UV waves Lower than UVAHealth risks Extremely low risk for DNA damage Can destroy Vitamin A in skin Can cause DNA damage, leading to skin cancer Responsible for sunburn
- 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 & FrequencyIn remote sensing, we sense and sample energy at different wavelengths and frequencies.These different frequencies tell us different things about the object being sensed.
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. As expected, visible light penetrates the easiest. Visible Light
. 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
Energy that strikes the Earths surface can beor all three.
Energy InteractionDifferent surfaces also reflect energy differently.
Have participants complete the Wavelength and Frequency worksheet prior to viewing this slideshow. They will come back to this sheet at Slide 6.***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.*Have participants look at their Wavelength and Frequency worksheet that was completed prior to the powerpoint.
The symbol for wavelength is lambda (). 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.*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)*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)*Which has the least energy? (radio waves)Which has the most energy? (gamma rays)
At the bottom of the graphic, note the change in EnergyFrequencyWavelength
Finishing the Wavelength and Frequency worksheet: Ask participants Which wave has the most energy and on what did you base your choice? (ii)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 illustration has the same orientation as the previous slide.)
What is a possible source of infrared radiation? (people or light bulb)Microwaves fall between Radio waves and Infrared Waves.***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.)*Why might ozone depletion cause a problem? (More UV rays, more damaging radiation, more skin cancers, crop damage, etc.) *Remember, ALL types of electromagnetic energy (light, radio waves, x-rays, etc) are categorized by wavelength and frequency.*The interaction of this ENERGY with the Earths surface (trees, sand, parking lot, water, etc.) is the basis for taking infrared measurements to Ground Truth remote images.**Youll see this when you do your infrared mapping.