Transcript What are some ways to produce light?

Unit 11 Lesson 5 Light Technology
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Unit 11 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.
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Unit 11 Lesson 5 Light Technology
Why are incandescent bulbs being
phased out?
• 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.
Last of incandescent light bulbs are banned
January 01, 2014|By Shan Li: LA Times
The final phase of a ban on incandescent light bulbs goes into effect
Wednesday, leaving consumers with pricier energy-efficient options that
are expected to save people money over time.
Beginning Jan. 1, the production of 40- and 60-watt incandescent light
bulbs is banned as part of efficiency standards signed into law by
President George W. Bush in 2007.
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Unit 11 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.
• Of the energy given off by
fluorescent bulbs, 80% is in
the form of visible light.
Fluorescent bulbs last 10 times
longer than incandescent light bulbs.
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Unit 11 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 11 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 11 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 11 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 11 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 11 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 11 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 11 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 11 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 11 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 11 Lesson 5 Light Technology
Seeing Is Believing
What are some ways light can change
what people see?
• 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 11 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 11 Lesson 5 Light Technology
What are some ways light can change
what people see?
• 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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