# General Wave Properties, the Electromagnetic Spectrum, and Astronomy - PowerPoint PPT Presentation

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## 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 that ... – PowerPoint PPT presentation

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Title: General Wave Properties, the Electromagnetic Spectrum, and Astronomy

1
General Wave Properties, the Electromagnetic
Spectrum, and Astronomy
• By
• Leslie McGourty and Ken Rideout
• All the information on waves thats fit to print

2
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)

3
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)

4
Transverse Waves
• Waves that travel perpendicular to the direction
of motion
•
• Examples Ocean waves, all forms of
electromagnetic energy

5
Wavelength
• Distance from one crest to the next crest (or
trough to trough)
• Measured in meters

6
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

7
WAVELENGTH AND FREQUENCY ARE INVERSELY RELATED
8
FREQUENCY AND ENERGY ARE DIRECTLY RELATED
9
WAVELENGTH AND ENERGY ARE INVERSELY RELATED
10
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

11
(No Transcript)
12
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

13
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)

14
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

15
X RAY ASTRONOMY
• X ray image of the night sky (can you spot the
disk of the Milky Way?)

16
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

17
ULTRAVIOLET ASTRONOMY
• Ultraviolet image of a distant galaxy
• Ultraviolet energy emitted by the sun

18
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

19
VISIBLE LIGHT PROPERTIES
20
VISIBLE LIGHT another view
21
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

22
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
• Used in remote controls,  surveillance, therapy
of muscles
• Sources  Humans, most astronomical objects

23
INFRARED ASTRONOMY
• Infrared image of the nucleus and coma of comet
Hale-Bopp
• Nebulae, like the Orion nebula, emit Infrared
energy

24
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

25
MICROWAVE ASTRONOMY
• This is a microwave image of the ENTIRE UNIVERSE
(from WMAP)

26
• 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

27
• The V.L.A. radio telescope array in New Mexico
• Radio-synthesized image of the Crab Nebula

28
Composite astronomy
• A complete picture of this Supernova remnant is
created by combining images from the different
types of electro-magnetic energy emitted

29
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!
30
• 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)

31
How light is used to determine the movement of
stars/galaxies
32
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