The Electromagnetic Spectrum Ppt

7/29/2019 The Electromagnetic Spectrum Ppt

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The ElectromagneticThe Electromagnetic

SpectrumSpectrum

Can you see me now?Can you see me now?

EE--M RadiationM Radiation

Each wavelength of electro-magneticradiation (light) brings us uniqueinformation.

Almost everything we know about theUniverse comes from the study of theelectromagnetic radiation emitted orreflected by objects in space.

Objects in space send out electromagneticradiation at all wavelengths - from gammarays to radio waves.

The electromagnetic spectrum can be expressedin different terms, or units:

Energy is measured in electron volts(eV).

Frequency is measured in cycles persecond (Hertz or Hz or kHz),

Wavelength is measured in meters(m) or nanometers (nm).


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Radio WavesRadio Waves

Have the longest wavelengths.Have the longest wavelengths.

These waves can be as long as aThese waves can be as long as a

mile.mile.

These are the same waves thatThese are the same waves that

carry signals for your televisioncarry signals for your television

and cellular phones.and cellular phones.

How do we "see" using RadioHow do we "see" using Radio

Waves?Waves?

Radio telescopesRadio telescopes::dishesdishesmade out of a conducting metalmade out of a conducting metalreflect radio waves to a focus point.reflect radio waves to a focus point.are much, much larger than an opticalare much, much larger than an opticaltelescope.telescope.are often combined into an array.are often combined into an array.often act together as one large telescope.often act together as one large telescope.

The Very Large Array (VLA), in New Mexico.

27, 81 ft diameter, radio telescopes work together.

The Arecibo site in Puerto Rico is embedded in limestone in thejungle.

The dish is over 1000 ft wide and uses the rotation of the Earth toexamine space.


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The Sun in radio waves How do we "see" usingHow do we "see" usingMicrowaves?Microwaves?

Cosmic BackgroundExplorer (COBE)

The Wilkinson MicrowaveAnisotropy Probe (WMAP)

Microwaves in SpaceMicrowaves in Space

This Cosmic Background Explorer(COBE) image is of the cosmicmicrowave background of the

visible universe. The pink and bluecolors show tiny fluctuations.

If you had a very sensitive microwavetelescope in your house you could detectfaint signals coming from all directions.

This is the Cosmic MicrowaveBackground!

The Sun in Microwave


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InfraredInfrared

Two categories:Two categories:

Far infrared" waves are thermalFar infrared" waves are thermaland are closer to the microwaveand are closer to the microwaveregion of the electromagneticregion of the electromagneticspectrum.spectrum.

"Near infrared" wavelengths are"Near infrared" wavelengths are

closer to visible light and are notcloser to visible light and are nothot at all.hot at all.

Infrared light isbetween visible lightand microwave.

The Sun in Infrared Light

The Orion constellation as seen in visible light and IR.

(Photos courtesy of JPLs Herschel Space Observatory Website)

Visible Light WavesVisible Light Waves

ROY G BIV


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Ca-K light(filtered)

White light(unfiltered)

The Sun in Visible Light Ultraviolet WavesUltraviolet Waves

UV is divided into three regions:UV is divided into three regions:

near ultravioletnear ultraviolet

far ultraviolet, andfar ultraviolet, and

extreme ultravioletextreme ultraviolet

Ultraviolet (UV) light waves are shorter visible light.Ultraviolet (UV) light waves are shorter visible light.

Three galaxies images in both visible and ultraviolet light.

NASA's Ultraviolet Imaging Telescope.

The Sun inExtreme Ultraviolet Light


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Sun in UV radiation. Sun in extreme UV.

XX--raysrays

Earth's atmosphere is so thick XEarth's atmosphere is so thick X--raysrays

cannot penetrate it.cannot penetrate it.

XX--ray telescopes are mounted onray telescopes are mounted on

satellites in space.satellites in space.

They are used to view high energyThey are used to view high energy

substances like black holes, supernovas,substances like black holes, supernovas,

and more.and more.

This is a photo of the Sun's X-ray radiation.


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The Sun in X-Rays GammaGamma--raysrays

Gamma-rays are the most

energetic.

They are produced by the

hottest regions of the universe.

The high-energy gamma photons pass right throughnormal telescope devices.

Gamma-ray telescopes map the energy path when agamma-ray strikes an electron and loses energy.

A computer processedimage of the CrabNebula in the "light" ofgamma-rays.

The Crab nebula wascreated by a supernovathat brightened the nightsky in 1054 A.D.


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Sun in Gamma

RadioRadioFarFar--InfraredInfraredMidMid--InfraredInfraredNearNear--InfraredInfrared

Visible: ColorVisible: ColorVLTVLT

Visible: DSSVisible: DSSUltravioletUltravioletXX--RayRay

Why Do We Have to Go to Space to SeeAll of the Electromagnetic Spectrum?

Atmospheric interference!

The Electromagnetic Spectrum Ppt

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