IMAGES FROM SPACE
Unit 4, Lesson 1
Pages 188-199
Electromagnetic Radiation
Energy traveling as electromagnetic waves (from the sun).
• Wavelength – the distance between two
adjacent crests or troughs of a wave
– The smaller the wavelength the more energy the
wave has
• Frequency – measures the number of waves
passing a point per second
– The higher-frequency wave carries higher energy
Electromagnetic Spectrum
• Spectrum – continuous range of a single
wavelength
• Electromagnetic spectrum
– Radio waves has the longest wavelength and
lowest frequency
• Televisions and radios use radio waves
• These receivers then produce sound waves
• Microwaves
• Infrared
– Sometimes called “heat radiation.”
• Visible light radiation
– You see an object when visible from the object
reaches your eyes. Ultrviolet
• Ultraviolet
– Wavelength shorter and contains more energy
– Frequency higher
– Energy powerful enough to kill living cells
• X-rays and Gamma Rays
– Shortest wavelengths
– Highest frequency
– Contain very high energy
– Can also kill living cells
Characteristics of Electromagnetic Radiation
• Electromagnetic waves can be generated by
cell phones, microwave ovens and flashlights
• They are also generated by heat
– Very cool materials radiate or emits energy mostly
radio waves
– Warmer objects may radiate mainly in the infrared
– To emit visible light, object must be hot.
• Light bulbs
• Microwave oven
–Microwaves penetrate a small
distance into many materials
where they are absorbed
–Energy is released as heat
• Ultraviolet
–Can cause materials to fluoresce
or glow
• Documents can be protected
against counterfeiting if they use
symbols that can be detected by
special lamps
• X-rays
–Pass through flesh easily by less
easily through bone
–Can be used to examine the insides
of your body
• In small amounts electromagnetic
radiation can be very useful
• Large amounts of any radiation can cause
problems
–Ultraviolet radiation – skin cancer
–Gamma rays - dangerous to living
organisms
What Electromagnetic radiation
reaches Earth?
• If Earth did not have an atmosphere
all electromagnetic radiation would
reach Earth
• Most radio and visible light radiation
reach Earth’s surface.
Detecting Electromagnetic Radiation
• All forms of electromagnetic radiation from
space can be collected by telescopes.
• Special detectors must be used to form
images from radiation other than visible light.
– Radio waves – Detected by radio telescopes
– Infrared, X-ray and Gamma ray detectors are used
for those higher frequency regions.
– Visible light - detected by optical telescopes
Optical telescopes
• Reflecting telescope – uses mirrors to collect
light
• Refracting telescope – uses lens to collect
light
• The larger the mirror or lens the more light
can be collected and the fainter objects can be
seen
Non-Optical Telescopes
• Radio telescopes – use metal mirrors to
reflect radio waves onto the antennae and
then to the computer to make an image.
–VLA – Very Large Array in New Mexico
has 26 movable radio telescopes
How can people observe Earth from
space?
• Remote Sensing Satellites – orbit at
different altitudes and directions
–Low Earth orbit satellites monitor the
atmosphere (a few hundred km)
–Take 90 min. to orbit the Earth once
• Geosynchronous - a satellite that
orbits about 36,000km above the
equator and it always stays above
the same location as Earth rotates
below it.
–Most weather observations are
made from satellites in this orbit.
What can you learn about Earth from satellite
images?
They show
• Evidence of human activity
• How things change over time
• Populated areas
• Highways
• Forest fires (warn people of danger)
• Images of clouds and storms (hurricanes)
• Auroras
• Ozone variations
What can you learn from space images?
• Visible light can show how objects in space
look.
• Infrared radiation can reveal temperatures of
objects.
• Infrared radiation can see what is behind dust
clouds.
• Some very bright objects are seen better using
an x-ray or gamma-ray telescopes.