The Electromagnetic Spectrum Waves a review p Most

The Electromagnetic Spectrum

Waves… a review p Most waves are either longitudinal or transverse. p Sound waves are longitudinal. p 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

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

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

EMS Wavelength …from shortest to longest

Short wavelength…high frequency Long wavelength…low frequency

Energy (from highest to lowest) shorter wavelengths & higher frequency = more energy decreasing wavelength 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: meaning: Rabbits
Meet
In
Very
Unusual
 Radio
Microwaves
In e. Xpensive
Gardens

- Have the longest RADIO WAVES 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 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 Red Orange Yellow Green Blue Indigo Violet Lowest Highest Frequency

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 p Extremely low risk for DNA damage p Can destroy Vitamin A in skin p Can cause DNA damage, leading to skin cancer p 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 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

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 …or all three. ENERGY

Energy Interaction Different surfaces also reflect energy differently.