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.