Unit 3 Lesson 5 Light Technology Copyright © Houghton Mifflin Harcourt Publishing Company

I Can See the Light What are some ways to produce light? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

What are some ways to produce light? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

What are some ways to produce light? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

What are some ways to produce light? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

Light Speed What are some ways light can transfer information? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

What are some ways light can transfer information? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

What are some ways light can transfer information? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

What are some ways light can transfer information? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

What are some ways light can transfer information? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

Light Work What are some ways light can interact with matter? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

What are some ways light can interact with matter? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

What are some ways light can interact with matter? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

What are some ways light can interact with matter? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

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. Copyright © Houghton Mifflin Harcourt Publishing Company

What are some ways light can change what people see? 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? Copyright © Houghton Mifflin Harcourt Publishing Company

What are some ways light can change what people see? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

What are some ways light can change what people see? 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. Copyright © Houghton Mifflin Harcourt Publishing Company