Unit 11 Lesson 5 Light Technology Copyright © Houghton Mifflin Harcourt Publishing Company.

Unit 11 Lesson 5 Light Technology

Copyright © Houghton Mifflin Harcourt Publishing Company

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.



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 bannedJanuary 01, 2014|By Shan Li: LA TimesThe 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.


http://articles.latimes.com/2014/jan/01


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.




• 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.




• 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.


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.



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.



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.



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.


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.



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.



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.



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.


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.



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.



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.


Unit 11 Lesson 5 Light Technology Copyright © Houghton Mifflin Harcourt Publishing Company.

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