the electromagnetic spectrum. most waves are either longitudinal or transverse. sound waves are...
TRANSCRIPT
The Electromagnetic Spectrum
Most waves are either longitudinal or transverse.
Sound waves are longitudinal.But all electromagnetic waves are
transverse…
Waves… 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 particles
• Can travel in a “vacuum” (they do NOT need a medium
– visible light
– radio waves
– microwaves
– infrared rays
– ultraviolet rays
– x-rays
– gamma rays
What 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 FrequencyWavelengthWavelength = Physical = Physical sizesize of wave of wave
FrequencyFrequency = = NumberNumber of waves in a given period of waves in a given period
Wavelength & FrequencyThe The shortershorter the wavelength… the wavelength…
……the the higherhigher the frequency. the frequency.
EMS Wavelength
…from shortest to longest
Long wavelength…low frequency
Short wavelength…high frequency
Energy (from highest to lowest)
shorter wavelengths & higher frequency = more energy
decreasing 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 Spectrum
Try:RabbitsMeetInVeryUnusualeXpensiveGardens
meaning: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
RADIO WAVES
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 missiles
Visible 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 VioletLowest HighestFrequency Frequency
ROY G. BIVROY 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
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.
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.
Although our eyes can directly Although our eyes can directly perceive only a small portion of the perceive only a small portion of the
electromagnetic spectrum...electromagnetic spectrum...
……we can gather more information by we can gather more information by using other portions of the EMSusing 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 Earth’s surface can be…
…or all three.
ENERGYReflected
Absorbed
Transmitted
Energy Interaction
Different surfaces also Different surfaces also reflect energy differently.reflect energy differently.