Unit 3 Lesson 5 Light Technology
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Unit 3 Lesson 5 Light Technology
I Can See the Light
What are some ways to produce light?
• Visible light produced from a very hot material is
incandescent light.
• Inside a typical incandescent bulb, electric current
is passed through a thin wire, called a filament.
The filament gets hot enough to emit, or give off,
visible light.
• Only about 8% of the energy given off by an
incandescent light bulb is in the form of light. The
rest is in the form of heat.
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Unit 3 Lesson 5 Light Technology
What are some ways to produce light?
• Electric current can energize some gases and
produce ultraviolet light, which is invisible to
humans.
• Fluorescent light is produced when a fluorescent
coating inside a bulb converts ultraviolet light into
visible light.
• 80% of the energy given off by fluorescent bulbs
is in the form of visible light. Fluorescent bulbs
last 10 times longer than incandescent light bulbs.
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Unit 3 Lesson 5 Light Technology
What are some ways to produce light?
• The tiny indicator light on many electronic devices
is a light emitting diode, or LED.
• LEDs contain solid material that emit light when
energized by an electric current.
• Almost 100% of the energy given off by LEDs is in
the form of visible light.
• Most traffic lights are now LEDs.
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Unit 3 Lesson 5 Light Technology
What are some ways to produce light?
• A laser is a device that produces intense light of a
very small range of wavelengths.
• Lasers produce light in such a way that causes the
light to be more concentrated, or intense, than
other types of light.
• Laser light is coherent. This means that the light
waves stay together as they travel away from
their source. The individual waves behave as one.
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Unit 3 Lesson 5 Light Technology
Light Speed
What are some ways light can transfer
information?
• Infrared radiation is invisible electromagnetic
radiation with a wavelength longer than human
eyes can detect.
• Space-based telescopes, weather satellites, and
some night vision goggles use infrared radiation to
collect data and help people see in the absence of
visible light.
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Unit 3 Lesson 5 Light Technology
What are some ways light can transfer
information?
• A thin, transparent glass thread that transmits
light over long distances is an optical fiber.
• Optical fibers are used to transmit information
through telephone cables and network computers.
• Optical fibers allow doctors to see inside a
patient’s body.
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Unit 3 Lesson 5 Light Technology
What are some ways light can transfer
information?
• Optical fibers are like pipes that carry light.
• Light stays inside an optical fiber because of total
internal reflection.
• Total internal reflection is the complete reflection
of light back and forth along the inside of the
material through which it travels.
• Light is then emitted out the end of the fiber.
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Unit 3 Lesson 5 Light Technology
What are some ways light can transfer
information?
• Satellites use electromagnetic waves to transmit
data.
• The Global Positioning System (GPS) is a network
of 24 satellites that orbit Earth and continuously
send microwave signals.
• GPS was originally used by the United States
military. Now, anyone who has a GPS receiver can
use the system.
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Unit 3 Lesson 5 Light Technology
What are some ways light can transfer
information?
• Satellites in orbit 20,000 km above Earth emit
microwaves that are detected by GPS Receivers.
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Unit 3 Lesson 5 Light Technology
Light Work
What are some ways light can interact
with matter?
• Doppler radar uses light in the form of radio
waves to measure weather patterns.
• Radio waves are sent out toward a weather
system.
• They bounce off the clouds and back to the
transmitter, which captures them for analysis.
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Unit 3 Lesson 5 Light Technology
What are some ways light can interact
with matter?
• The frequency of the radio waves changes a small
amount, depending on how the weather system is
moving.
• Reflected radio waves are received, and the image
is used to make a picture of the entire moving
weather system.
• The speed and intensity of the moving system can
be determined.
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Unit 3 Lesson 5 Light Technology
What are some ways light can interact
with matter?
• Light from lasers can be accurately pointed and be
used to melt and cut different materials.
• Lasers can be used to cut, weld, and engrave
certain metals.
• Lasers are used to shape the cornea of the eye to
correct eyesight.
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Unit 3 Lesson 5 Light Technology
What are some ways light can interact
with matter?
• Lasers are also used in the CD drives of
computers and in many printers.
• Laser pointers can be used from a distance. Laser
levelers can help you hang pictures in a straight
line.
• Lasers are also used to make holograms.
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Unit 3 Lesson 5 Light Technology
Seeing Is Believing
What are some ways light can change
what people see?
• Microscopes are used to see magnified images of
tiny, nearby objects.
• Simple light microscopes have two convex lenses.
• An objective lens is close to the object being
studied. An eyepiece lens is the lens you look
through.
• Light from a lamp or mirror at the bottom shines
through the object being studied.
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Unit 3 Lesson 5 Light Technology
What are some ways light can change
what people see?
• Where are the two lenses found in a microscope?
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Unit 3 Lesson 5 Light Technology
What are some ways light can change
what people see?
• Telescopes are used to see images of large,
distant objects.
• Telescopes that use visible light are classified as
either refracting or reflecting.
• Refracting telescopes use lenses to collect light,
while reflecting telescopes use mirrors to collect
light.
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Unit 3 Lesson 5 Light Technology
What are some ways light can change
what people see?
• Cameras are used to record images, both moving
and still.
• A digital camera controls the light that enters the
camera and uses sensors to detect the light.
• The sensors send electrical signals to a computer
in the camera. These signals contain data about
the image that can be stored and transferred.
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