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Electromagnetic Spectrum
Properties of EM Waves
 EM Waves have frequency, amplitude, wavelength
and speed
 Almost all EM Waves are invisible with the exception
of visible light
 The entire range of EM Waves is called the
Electromagnetic Spectrum
NASA Introduction
 Watch this You Tube video from NASA
EM Spectrum
Another EM Diagram
Practical Uses of EM Waves
 Radio Waves
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Lowest energy and lowest frequency
Wavelength ranges of Km down to tens of centimeters
Used with communications
 Microwaves:
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30 cm to 1 mm
Microwaves transfer energy to water molecules in
food
 Infrared waves:
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Radiant heat/cannot see it but you can feel it
Thermal imaging
Practical Uses Continued:
 Ultraviolet Light:
 Contained in sunlight
 Small amounts can be beneficial, larger amounts can
cause cancer and sunburns
 X-Rays:
 Used exclusively in medicine
 Bone images absorb the Rays and that is why they
appear darker on the image
 Gamma Rays:
 Generated in nuclear reactions
 Very dangerous without protection
WAVELENGTH AND FREQUENCY
REMEMBER
The wavelength of a wave and
the frequency of the wave are
inversely related; as one
increases, the other decreases
Speed of Light
 The speed of light AND all electromagnetic
waves is constant when in a vacuum.
 The speed of light is a constant value of:
3 x 108 m/sec.
 The speed of light is represented by a constant
of:
C
Light can act like a wave!
 It can reflect!
Reflection = bouncing off
Light can act like a wave!
 It can refract!
Refraction = bending when
it passes through
Light can act like a wave!
 It can disperse!
Dispersion = separating
frequencies of light
LIGHT AND THE DOPPLER EFFECT
 Newton observed the prism effect of light in 1665
 In the late 19th century it was noted that chemicals
produce a spectrum when heated
LIGHT AND THE DOPPLER EFFECT
 This led to the discovery of the following…
 When a light source is moving toward an object the
wavelengths appear shorter

When a light source is moving away from an object
the wavelength appear longer
Moving away…light waves shift to RED
Moving toward…light waves shift to BLUE
This shift in wavelengths is the DOPPLER EFFECT
This is strong support for The Big Bang Theory
The Red Shift and Blue
Shift allow Astronomers
to calculate the speed and
direction that stars and
galaxies are moving.
DOPPLER
Timeline Project
 Create a Timeline Poster
 Start in the 1700’s and progress to
present day
 Identify and explain the relevant
space technologies invented
 Include pictures when possible
 Complete on paper provided
Understanding Space Timeline
THE BIG BANG THEORY
 Observations of RED SHIFT led to the theory
of the expanding universe
 This theory stated that…
 17
billion years ago a “Big Bang” sent all
the matter and energy outward in a cloud
 Cloud expanded into clumps
 Clumps evolved into galaxies
 Universe is still expanding outward
Hubble’s Law
 Edwin Hubble discovered that most galaxies
are moving away from Earth
 They are also moving away from each other
 Hubble discovered a relationship and a law
was created
 Hubble’s Law states that the further
away the galaxy, the faster it is moving
away from us
 This is strong support for Big Bang
STARS AND GALAXIES
 A star is…
A
body of gases that gives off a
tremendous amount of radiant
energy in the form of light and heat
 Stars
vary in size, mass and color
STARS/ORION
STELLAR MAGNITUDES
Apparent Magnitude
 Brightness of a star as
it appears from Earth
 Related to the distance
and light emitted
 Powerful telescopes
measure brightness
and assign a number
Absolute Magnitude
 True brightness of star
if it were 32.6 light
years away
CLASSIFICATION OF STARS
 The Hertzsprung-Russell diagram is a
chart that astronomers use to classify
stars
 The chart/graph plots stars’ absolute
magnitude and temperature to create
a classification system
H-R Diagram
H-R Diagram Trends
 The brightness of most stars increases as
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their surface temperature increases
The majority of stars fall within a band called
the “Main Sequence”
Our sun is a “Main Sequence” star
Upper right hand corner of chart has large,
bright and cool stars called “Super Giants”
Bottom left hand corner has the very small,
dim and hot stars called “White Dwarfs”
A Star is Born!
 All Stars begin their lives as part of a NEBULA
 A NEBULA is a large cloud of gas and dust spread
out over a great distance.
 Gravity causes the cloud to contract and become
dense and hot
 Temperature increases so that nuclear fusion
starts at the core and this is the formation of a
star
 You tube video: Life of a Star
Life Cycle
How Long Does a Star Live?
 The life span of a star depends on its size
 The larger stars have a shorter life
 The smaller stars have a longer life
WHY
 The smaller stars are more efficient in using
the fuel that they have
The Death of a Star
 When a star runs out of fuel, its inner core
starts to shrink
 The outer portion of the core starts to expand
 Once the fuel is gone, the star will become a…
White Dwarf
 A Neutron Star
 A Black Hole

 Compare and Contrast the life
cycles of the medium mass
and large mass stars
 Remember to discuss
similarities and differences