Electromagnetic Waves

Students will be able to

Describe polarity

Reproduce the entire spectrum

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Where?

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What is an Electromagnetic Wave

Wave that transfers energy without a medium

Vibration of electric and magnetic fields that move through space at the speed of light

Created by moving an electric charge

Called electromagnetic radiation

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Speed

Speed in a vacuum 300,000 kilometers per second

From sun to Earth?

8 minutes

Light slows down when it enters a medium

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Models

Wave Model

Light travels in many directions at once

Polarizing filters block all but light in one direction

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Models

Particle Model

Light is a tiny particle moving through space

Called photon

Light bump up electrons in atoms

Called photoelectric effect

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Electromagnetic Spectrum

All electromagnetic waves travel at same speed

Vary only in wavelengths and frequencies

Waves you can see are called visible light

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Radio Waves

Long wavelength

Low frequency

Purpose

Broadcast Waves for TV and Radio

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Microwaves

Shortest radio waves

Cell phones

Radar (Radio Detection And Ranging)

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Infrared Rays

Heat waves that you feel but can not see

Heat Lamps

Infrared Cameras

Warmer objects give off more waves than cold

Satellites

Locate people

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Visible Light

Small part of electromagnetic spectrum

Longest waves = Red

Shortest waves = Violet

Visible light is a mixture of all wavelengths – White

When bending in a new medium red bends leastThe color you see is what is reflected

(rest of light is absorbed)

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Ultraviolet Rays

Much shorter waves than visible light (more energy)

Very dangerous

Cause damage

Cancer cells

Eye damage

Kill bacteria (used in hospitals/labs)

Sunscreen and sunglasses used to black these rays

Ozone layer blocks many of these rays

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X-Rays

High energy

Penetrates most tissues

Blocked only by very dense structures

Bone / Lead

Used in medicine and structural analysis to look for damage

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Gamma Rays

Extremely high energy

Used in medicine to kill cancer cells

Can not penetrate Earth atmosphere

Telescopes put into space to detect

Discovery of astronomical events

Stars, black holes, galaxies…

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Review

• Polarization

• Spectrum– Radio Waves– Microwaves– Infrared– Visible Light– Ultraviolet– X-Ray– Gamma

Quiz

Homework

Draw and label the electromagnetic spectrum. Describe one thing of importance for each part of the spectrum.