General Wave Properties, the Electromagnetic Spectrum, and Astronomy

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General Wave Properties, the Electromagnetic
Spectrum, and Astronomy

• By
• Leslie McGourty and Ken Rideout
• (modified by your teacher)
• All the information on waves thats fit to print

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What is a wave?

• A wave is a transfer of energy from one point to
  another via a traveling disturbance
• A wave is characterized by its wavelength,
  frequency, and amplitude
• There are 2 main types of waves longitudinal
  (like sound) and TRANSVERSE (like electromagnetic
  waves)

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Why do we care about waves?

• Because the best way to learn about astronomical
  objects such as STARS, GALAXIES, AND BLACK HOLES
  that are MANY TRILLIONS OF MILES AWAY is to study
  the ELECTROMAGNETIC ENERGY WAVES THAT THEY EMIT
  (give off)

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Transverse Waves

• Waves that travel perpendicular to the direction
  of motion
•               
• Examples Ocean waves, all forms of
  electromagnetic energy

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Wavelength

• Distance from one crest to the next crest (or
  trough to trough)
• Measured in meters

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Frequency

• Number of crests passing by a given point per
  second
• Measured in Hertz (Hz) defined to be one cycle
  per sec
• Equal to the inverse of the amount of time it
  takes one wavelength to pass by

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WAVELENGTH AND FREQUENCY ARE INVERSELY RELATED
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FREQUENCY AND ENERGY ARE DIRECTLY RELATED
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WAVELENGTH AND ENERGY ARE INVERSELY RELATED
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Electromagnetic Waves

• Waves of energy that have both electrical and
  magnetic properties
• Any object that is above absolute zero emits
  electromagnetic waves
• The entire group of waves with these properties
  is called the Electromagnetic Spectrum
• Still confused? Then click What are
  electromagnetic waves?
• To move onto the EM spectrum click

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The Electromagnetic Spectrum

• Think you know all about the electromagnetic
  spectrum? Well take a tour of the Electromagnetic
  Spectrum to find out more cool information.
• The Following slides show and explain the
  different types of Electromagnetic Radiation

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TYPES OF ELECTROMAGNETIC WAVES

• GAMMA RAYS
• Emitted from the nuclei of atoms during
  radioactive decay or during high-speed collisions
  with particles.
• Sources Black holes, stars, supernovae
• Used in cancer treatment and for sterilization
  Sources Cobalt 60, the inner core of the sun

• Gamma ray image of The center of the Milky Way
  (where a black hole resides)

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X-RAYS

• Emitted when an electron that is moving very
  quickly is suddenly stopped , or
• emitted by heavy atoms after bombardment by an
  electron
• Used for radiography (x-ray photography) and to
  look at materials in industry for defects

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X RAY ASTRONOMY

• X ray image of the night sky (can you spot the
  disk of the Milky Way?)

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ULTRAVIOLET RAYS

• Above the color violet 
• Three groups - UV A, UV B, and UV C.
• A type longest wavelength least harmful
• UV B and UV C are absorbed by DNA in cells 
• Used by the body to produce vitamin D, to kill
  bacteria on objects, and for sun tanning
• Sources   Ultra hot objects 5000C or more, such
  as Stars

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ULTRAVIOLET ASTRONOMY

• Ultraviolet image of a distant galaxy

• Ultraviolet energy emitted by the sun

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VISIBLE LIGHT

• White light combination of all the colors
• Rainbow white light that has been separated into
  a continuous spectrum of colors
• Used for communications
• (fiber optics)
• Sources  very hot objects (stars, galaxies)

• Galaxies emit enough visible light to be seen
  from great distances

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VISIBLE LIGHT PROPERTIES
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VISIBLE LIGHT another view
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VISIBLE LIGHT ASTRONOMY

• The Eagle Nebula a massive Star forming cloud
  within the Milky Way
• Each column of dense gas/dust is many Trillions
  of miles tall

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INFRARED

• Below Red visible light
• Thought of as heat but is not always
• Far infrared energy is heat energy.
• All objects that have warmth radiate infrared
  waves
• Easily absorbed and re-radiated. 
• Used in remote controls,  surveillance, therapy
  of muscles
• Sources  Humans, most astronomical objects

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INFRARED ASTRONOMY

• Infrared image of the nucleus and coma of comet
  Hale-Bopp

• Nebulae, like the Orion nebula, emit Infrared
  energy

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MICROWAVES

• The microwave image below (from COBE) helped to
  prove the Big Bang Theory

• 1 mm-1 dm in length
• Absorbed by water molecules how microwave ovens
  heat food
• Used in tele-communications and power
  transmission
• Sources  electric circuits, microwave ovens,
  stars

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MICROWAVE ASTRONOMY

• This is a microwave image of the ENTIRE UNIVERSE
  (from WMAP)

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RADIO WAVES

• 10 cm- 100,000m  in length
• Only cosmic waves the reach the surface of the
  Earth
• Cause of noise
• Divided into smaller frequency dependent groups
  called bands  
• Used for communications, gadgets- cell phones,
  microwaves, remote controls, garage door openers
• Sources  transmitters and sparks from motors,
  stars, black holes
• Science- radio astronomy, atmospheric research

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RADIO ASTRONOMY

• The V.L.A. radio telescope array in New Mexico

• Radio-synthesized image of the Crab Nebula

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Composite astronomy

• A complete picture of this Supernova remnant is
  created by combining images from the different
  types of electro-magnetic energy emitted

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HOW TO IDENTIFY THE COMPOSITION OF OBJECTS

• Hydrogen
• Helium
• Carbon
• Iron

When heated, each element emits its own unique
and distinct pattern of wavelengths of light.
This is known as a SPECTRAL FINGERPRINT. By
using a database of these fingerprints,
astronomers can identify the composition of a
distant object. For example, the spectral pattern
produced by a star is shown below. It matches
the spectral fingerprint of Hydrogen therefore,
we now know that the star is composed of Hydrogen
gas!
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• The 3 types of spectra
• Coninuous solid rainbow solids and ionized
  gases (random electrons)
• Absorption when white light passes through a
  cool gas black lines appear in spectrum show
  missing lines absorbed by gas shows gas
  identity
• Emission by heated gases (fingerprints)

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How light is used to determine the movement of
stars/galaxies
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How light is used to detect invisible alien
planets
By measuring the cyclical Doppler shift of a
star, astronomers can figure out how far the star
is wobbling, which allows them to figure out THE
MASS OF ITS ORBITING PLANET, AND ITS DISTANCE
FROM THE STAR