Electromagnetic (EM) waves are invisible forms of energy that travel though the universe

Electromagnetic Waves Why are they called electromagnetic? Electromagnetic waves are formed when an electric field (which is shown in red arrows) couples with a magnetic field (which is shown in blue arrows).

Types of EM Waves All EM waves fall into one of the following types: +Radio Waves +Micro Waves +Infrared Waves +Visible Light Waves +Ultra Violet Waves +X-Ray Waves +Gamma Ray Waves 104 10-4 10-2 1 102 10-12 10-10 10-8 10-6 Wavelength  (m) 108 106 1012 1014 1010 1018 1020 1016 Frequency (Hertz) Radio & Television Radar Infra Red Ultra Violet x-Rays Gamma Rays AM Radio FM Radio Television Orange Red Yellow Green Blue High Energy Low Energy

Waves in the electromagnetic spectrum vary in size from long radio waves the size of buildings, to very short gamma-rays smaller than the size of the nucleus of an atom.

Radio waves Longest wavelength EM waves Uses: TV broadcasting AM and FM broadcast radio Avalanche beacons Heart rate monitors Cell phone communication Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Microwaves Wavelengths from 1 mm- 1 m Uses: Microwave ovens Bluetooth headsets Broadband Wireless Internet Radar GPS Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Infrared Radiation Wavelengths in between microwaves and visible light Uses: Night vision goggles Remote controls Heat-seeking missiles Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Visible light Only type of EM wave able to be detected by the human eye Violet is the highest frequency light Red light is the lowest frequency light Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Isaac Newton was the first to figure out that white light can be separated into the visible full spectra of colors because different wavelengths of light travel at different speeds when going from one medium to another

Ultraviolet Shorter wavelengths than visible light Uses: Black lights Sterilizing medical equipment Water disinfection Security images on money There is one more UV slide…

X-rays Tiny wavelength, high energy waves Uses: Medical imaging Airport security Inspecting industrial welds Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Gamma Rays Smallest wavelengths, highest energy EM waves Uses Food irradiation Cancer treatment Treating wood flooring Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Temperature and the EM Spectrum Shorter wavelengths of the EM spectrum have higher temperatures

Wave Properties The main properties of a wave can be defined using the following vocabulary: Frequency Wavelength Amplitude Speed

Frequency Frequency is defined as the number of waves that pass a certain point in a second.(waves per second)

This is a shorter wavelength This is a longer wavelength Wavelength is defined as the distance from the crest of one wave to the crest of the next. (Also called the wave period) This is a shorter wavelength This is a longer wavelength

Wavelength Notice the wavelength is long (Radio waves) and gets shorter (Gamma Rays)

Amplitude Amplitude Is the height of the wave and it is reflective of the power of a wave Both of the waves below have the same wavelength but the one on the right has the greater amplitude Amplitude An audio amplifier amplifies the strength of the electrical signal which then amplifies the height of the sound wave making a louder sound. ROCK ON!

Speed of an EM wave Speed of a wave is calculated by multiplying the frequency x wavelength The speed of the electromagnetic spectrum is the speed of light Speed of light = 3x108 m/s or 186,000 miles/second

Stars & EM Waves When stars go through the process of nuclear fusion, EM waves are created and the energy is released as a photon of light All of the EM waves produced by stars are invisible to us accept visible light A photon is a little packet of light energy that behaves as a wave and a particle

The Sun at Different Wavelengths Visible Ultraviolet Radio X-ray

Electromagnetic radiation from space is unable to reach the surface of the Earth except at a very few wavelengths, such as the visible spectrum, radio frequencies, and some ultraviolet wavelengths.

Clicking the little rainbow box at the top of each slide will bring you back to this one

EM Spectrum Video (5 min) http://www.youtube.com/watch?annotation_id=annotation_616509&feature=iv&src_vid=YgQQb1BVnu8&v=cfXzwh3KadE

EM Waves as a Tool for Astronomers There are 3 main types of visible spectrums that can tell us what elements objects are made up of: Continuous spectrum Continuous Spectrum – White light producing Full ROYGBV spectra

Emission or bright line spectrum Bright Line Spectrum – the spectrum of an element heated to a temperature where it glows and produces light (incandescent) and appearing as one or more bright lines. (Like fingerprints, all elements have a unique signature of lines)

Absorption or dark line spectrum Absorption Spectrum – When white light passes through ionized gas or vapor the wavelength of the gasses elemental composition is absorbed and the rest passes through to the observer

The outer layers of a star are nothing more then hot gas.

How are the absorption and emission lines similar and different?

Hydrogen Absorption (Dark Line) & Emission (Bright Line) Spectra

How do we interpret an actual spectrum? By carefully studying the features in a spectrum, we can learn a great deal about the object that created it.

What is this object? Reflected Sunlight: Continuous spectrum of visible light is like the Sun’s except that some of the blue light has been absorbed - object must look red

What is this object? Thermal Radiation: Infrared spectrum peaks at a wavelength corresponding to a temperature of 225 K

What is this object? Carbon Dioxide: Absorption lines are the fingerprint of CO2 in the atmosphere

What is this object? Ultraviolet Emission Lines: Indicate a hot upper atmosphere

What is this object? Mars!

Doppler Effect- the change in frequency of a wave for an observer moving relative to its source. This effect can be heard with sound waves The noise of a passing siren falls in pitch as it passes. This is due to the stretching of the sound waves behind the vehicle and the compression of sound wavehe Doppler Effect.

Visible Spectrum Doppler Shift In Light This effect can also be seen in the visible spectrum of light waves! -The motion of an object traveling away from us produces a shift towards the red end of the spectrum of light due to a stretching of the light waves. -The Motion of an object traveling toward us produces a shift towards the blue end of the spectrum of light due to compressing of the light waves. -As a result, objects traveling towards us look more blue and objects traveling away from us look more red. Red Orange Yellow Green Blue Indigo Violet Visible Spectrum

Doppler effect of light can be remembered by thinking of a car heading towards or away from you.

This light source is moving away at 15,000 mile per hour By measuring the amount that dark lines shift, scientists can calculate how fast objects are moving toward or away. This light source is moving away at 15,000 mile per hour This light source is moving away at 94,000 mile per hour This light source is not moving away at all.

Reading a Spectrascope. For this Bright Line Spectrum there are three lines. a thick blue line at approximately 445 a green at approximately 525 A red line at approximately 635

Fluorescent light bulb Emission Spectrum What frequency of waves are the 5 lines?

The Spectrum of the Sun

Emission (Bright Line) Spectra

Krypton Gas

Bright Line Spectrum Hydrogen Helium Carbon Nitrogen Krypton