Sunday, December 25, 2011
8th Grade Unit #3 Wave Interactions
WAVE INTERACTIONS
VSC CONTENT INDICATORS AND OBJECTIVES |
5. 6. D. WAVE INTERACTIONS A wave is a disturbance that travels either through a medium (mechanical waves, such as sound waves) or through space (electromagnetic waves, such as light waves). |
· Wave is a disturbance or variation that carries energy progressively from point to point in a medium or space without transporting matter.
· Mechanical waves move through a medium where the particles collide back and forth in oscillations or vibrations to transfer kinetic energy but the medium itself does not flow with it.
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BIG IDEAS
Examples of mechanical waves are waves on a string and sound waves.
· Electromagnetic wave is a wave of energy consisting of electric and magnetic fields, oscillating at right angles to each other. These waves disturb electric and magnetic fields instead of particles. Electromagnetic waves can be transmitted through a vacuum.
· Electromagnetic waves form a spectrum of energy from low to high frequency which includes radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, x-rays, and gamma radiation.
· Wave-particle duality describes the idea that particles can act like waves, and waves can act like particles. Light is an electromagnetic wave that acts like waves and particles.
· Sound is produced when an object vibrates, causing a transfer of kinetic energy through a medium.
· In a longitudinal wave the particles of the medium vibrate back and forth in a direction which is parallel and anti-parallel to the direction of energy transport.
· In transverse waves, the vibration of the medium is perpendicular to the motion of the wave.
· Sound can exist as either a longitudinal or transverse wave in solids. But in liquids and gases, sound can only exist as a longitudinal wave.
· Examples of transverse waves include seismic S (secondary) waves, a ripple on a pond, and a wave on a string.
· The transfer of kinetic energy through a medium produces a series of compressions and rarefactions.
· Compressions are areas where the surrounding molecules are crowded together in the medium where wave is propagated.
· Rarefactions are areas where the molecules are spread out in the medium where wave is propagated.
Sound is vibrations and has the properties or volume, pitch, and quality.
ASSIGNMENT=Please copy these questions into your journal and answer the questions there
PRE TEST- Waves and Rays, Part I
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False
True
Energy that is created only by the sun
Energy that is created by atoms and electricity |
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ASSIGNMENT=PLEASE WATCH THIS VIDEO BELOW AND TAKE 10-15 NOTES IN YOUR JOURNAL
First Big Assignment=
VOCABULARY WORDS TO LOOK UP AND PUT IN YOUR JOURNAL
Wave
Mechanical wave
Electromagnetic wave
Transverse wave
Surface wave
Longitudinal wave
Crest
Trough
Compression
Rarefaction
Energy
Medium
Vibration
Amplitude
Frequency
Wavelength
Hertz
Reflection
Refraction
Diffraction
Seismic wave
Primary wave
Secondary wave
Light
Sound
Earthquake
Elasticity
Density
Speed
Intensity
Loudness
Decibels
Doppler Effect
Sonar
Sonogram
Echolocation
Noise
Electromagnetic radiation
Waves and Rays, Part I By Cindy Grigg | |
1 Have you ever played in the ocean? The waves can push you around. They can pull the sand out from under your feet. As far out as you can see, there are more waves coming at you all the time.2 There are other kinds of waves all around you all the time. You can't see most of them, but they can warm you, burn you, and go right through your body. These are the waves of the electromagnetic spectrum.
3 These waves come from the same kind of electric force that makes your TV work and from the same kind of magnetic force that holds the picture you drew in art class on your kitchen refrigerator with a magnet. When these two forces act together, they make electromagnetic radiation. This is a kind of energy that is both electric and magnetic. This energy travels in waves.
4 In some ways, these waves and ocean waves are alike. They have tops called crests. They have bottoms called troughs. The distance from one crest to the next is called a wavelength. Wavelengths can also be measured from one trough to the next. Another way electromagnetic (EM) waves are like ocean waves is that they both move energy from one place to another.
5 The biggest difference between ocean waves and EM waves is that ocean waves move across water. Energy moves through the water. EM waves don't need anything to move through. They can move across the emptiness of outer space. In outer space where there is nothing for the waves to move through, the waves travel at the speed of light. EM waves can also travel through things. They can travel through air inside a room, around the earth, or through food. Some EM waves can even travel inside your body!
ASSIGNMENT=Please copy the graphic organizer into your journal and complete it from the reading above in the journal
6 Let's learn more about these mysterious waves. When you turn on a radio, you're using part of the EM spectrum. Radio waves have the longest wavelengths of any of the waves in the EM spectrum. Radio waves can be several miles long, or they can be about the length of a one-foot ruler.
7 When you turn the dial on the radio, you are changing from one radio frequency to another. Frequency means how many waves pass a certain point in one second. If you could see radio waves, you could stand on the street outside your house and count them. Imagine there is a radio tower at the end of your street. The tower sends out radio signals. If you could see the radio waves, you could count how many of them pass a point in front of you in one second. A single wave from one crest to the next (or one trough to the next) is called a cycle. If five thousand waves passed the point in front of you in one second, the radio signal would have a frequency of five thousand cycles per second. You'd have to be able to count pretty fast!
Please explain what Frequency is in your journal in 2-3 sentences.
Please explain what a "cycle" is in your journal in 2-3 sentences.
8 Another name for cycle per second is hertz. It is abbreviated Hz. Radio waves are used to broadcast radio and TV shows and signals for cellular phones, pagers, and beepers. They carry signals here on Earth and through outer space.
9 There are seven different types of EM. The frequency of the waves makes each type different. Frequency is the number of cycles that pass a given point in one second. The example above (where you counted radio waves from a tower) had a frequency of five thousand cycles per second. Waves in the EM spectrum that have the lowest frequencies have the least amount of energy. Waves with the highest frequencies have the most energy. The first type we learned about is radio waves. The other six types are microwaves, infrared, visible light, ultraviolet, X rays, and gamma rays.
ASSIGNMENT=Please copy the graphic organizer into your journal and complete it from the reading above in the journal
10 Microwaves are shorter waves than radio waves - shorter than 11.8 inches. The ones used in microwave ovens to cook food are about five inches long. How do microwaves cook food? When you put food into a microwave, the plate stays cool and the food gets hot. Inside food is water. Plates don't have water inside them. When the microwaves hit the food, the water inside the food begins to vibrate from the energy. Microwaves have a frequency of two billion four hundred fifty million waves per second. The water molecules vibrate with that same frequency. When molecules vibrate, they move. The movement releases heat inside the food. The heat cooks the food very quickly.
11 Two billion four hundred fifty million waves per second is a really big number. Scientists needed a shorter way to say it. A million cycles is a megahertz, abbreviated MHz. A thousand megahertz, or 1000 MHz, is the same as saying one billion cycles per second. The frequency of a microwave can be written as 2450 MHz. Microwaves are also used for communication and TV satellites and for radar. These have shorter waves than those used for microwave ovens. Communications satellite microwaves can be as short as four-hundredths of an inch. When a wavelength is that short, the frequency is high - three hundred billion cycles per second. This can be written as 300 GHz, or 300 gigahertz. "Giga" means one billion.
12 Infrared waves are the next ones in the band of EM radiation. If you stand in the sunlight, you can feel warmth from the sun's infrared radiation. Your TV remote works on infrared waves. When you push a button on your TV remote, a microchip in the remote starts a vibration. It produces waves in the infrared range. Infrared waves have frequencies of 100 billion to 100 trillion cycles per second. Here's another prefix to learn: "tera" means one trillion. One terahertz (THz) is one trillion hertz or cycles per second. Since the frequencies of infrared beams are so high, the wavelengths are short-from four-hundredths of an inch to only four-hundred thousandths of an inch.
13 These infrared beams carry codes. Inside the TV set, another microchip identifies each code and sends a signal to raise or lower the volume, change channels, turn the set on or off, record a program, or do whatever you want it to do. Firefighters use infrared cameras to look through smoke and find survivors. They are used in building construction to find heating and cooling system leaks. They are also used in medicine to diagnose cancers and injuries, similar to X-rays.
14 Radio, microwaves, and infrared are only part of the waves that make up the EM spectrum. Read Waves and Rays, Part II to find out more.
Copyright © 2011 edHelper
ASSIGNMENT= Please click this website about radio waves and explain @ what you see in your journal http://www.nrao.edu/images/lera/em_anim.gif
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Waves and Rays, Part I
ASSIGNMENT=Please copy these questions into your journal and answer the questions there
Waves and Rays, Part I By Cindy Grigg | |
Directions: Fill in each blank with the word that best completes the reading comprehension.
Have you ever played in the ocean? The waves can push you around. They can pull the sand out from under your feet. As far out as you can see, there are more waves coming at you all the time.There are other kinds of waves all around you all the time. You can't see most of them, but they can warm you, burn you, and go right through your body. These are the waves of the (1) _______________________ spectrum.
These waves come from the same kind of electric force that makes your TV work and from the same kind of magnetic force that holds the picture you drew in art class on your kitchen refrigerator with a magnet. When these two forces act together, they make electromagnetic radiation. This is a kind of energy that is both electric and magnetic. This energy travels in waves.
In some ways, these waves and ocean waves are alike. They have tops called crests. They have bottoms called troughs. The distance from one crest to the next is called a (2) _______________________ . Wavelengths can also be measured from one trough to the next. Another way electromagnetic (EM) waves are like ocean waves is that they both move energy from one place to another.
The biggest difference between ocean waves and EM waves is that ocean waves move across water. Energy moves through the water. EM waves don't need anything to move through. They can move across the emptiness of outer space. In outer space where there is nothing for the waves to move through, the waves travel at the speed of light. EM waves can also travel through things. They can travel through air inside a room, around the earth, or through food. Some EM waves can even travel inside your body!
Let's learn more about these mysterious waves. When you turn on a radio, you're using part of the EM spectrum. Radio waves have the longest wavelengths of any of the waves in the EM spectrum. Radio waves can be several miles long, or they can be about the length of a one-foot ruler.
When you turn the dial on the radio, you are changing from one radio frequency to another. Frequency means how many waves pass a certain point in one second. If you could see radio waves, you could stand on the street outside your house and count them. Imagine there is a radio tower at the end of your street. The tower sends out radio signals. If you could see the radio waves, you could count how many of them pass a point in front of you in one second. A single wave from one crest to the next (or one trough to the next) is called a cycle. If five thousand waves passed the point in front of you in one second, the radio signal would have a frequency of five thousand cycles per second. You'd have to be able to count pretty fast!
Another name for cycle per second is (3) _______________________ . It is abbreviated Hz. Radio waves are used to (4) _______________________ radio and TV shows and signals for cellular (5) _______________________ , pagers, and beepers. They carry signals here on Earth and through outer space.
There are seven different types of EM. The frequency of the waves makes each type different. Frequency is the number of cycles that pass a given point in one second. The example above (where you counted radio waves from a tower) had a frequency of five thousand cycles per second. Waves in the EM spectrum that have the(6) _______________________ frequencies have the least amount of energy. Waves with the highest frequencies have the most energy. The first type we learned about is radio waves. The other six types are microwaves, infrared, visible light, ultraviolet, X rays, and gamma rays.
Microwaves are shorter waves than radio waves - shorter than 11.8 inches. The ones used in microwave ovens to cook food are about five inches long. How do microwaves cook food? When you put food into a microwave, the plate stays cool and the food gets hot. Inside food is water. Plates don't have water inside them. When the microwaves hit the food, the water inside the food begins to vibrate from the energy. Microwaves have a frequency of two billion four hundred fifty million waves per second. The water molecules vibrate with that same frequency. When molecules vibrate, they move. The movement releases heat inside the food. The heat cooks the food very quickly.
Two billion four hundred fifty million waves per second is a really big number. Scientists needed a shorter way to say it. A million cycles is a (7) _______________________ , abbreviated MHz. A thousand megahertz, or 1000 MHz, is the same as saying one billion cycles per second. The frequency of a microwave can be written as 2450 MHz. Microwaves are also used for (8) _______________________ and TV (9) _______________________ and for radar. These have shorter waves than those used for microwave ovens.(10) _______________________ (11) _______________________ microwaves can be as short as four-hundredths of an inch. When a wavelength is that short, the frequency is high - three hundred billion cycles per second. This can be written as 300 GHz, or 300 (12) _______________________ . "(13) _______________________ " means one billion.
Infrared waves are the next ones in the band of EM radiation. If you stand in the sunlight, you can feel warmth from the sun's infrared radiation. Your TV remote works on(14) _______________________ waves. When you push a button on your TV remote, a microchip in the remote starts a vibration. It produces waves in the infrared range. Infrared waves have frequencies of 100 billion to 100 trillion cycles per second. Here's another prefix to learn: "tera" means one trillion. One terahertz (THz) is one(15) _______________________ hertz or cycles per second. Since the frequencies of infrared beams are so high, the (16) _______________________ are(17) _______________________ four-hundredths of an inch to only four-hundred thousandths of an inch.
When you turn the dial on the radio, you are changing from one radio frequency to another. Frequency means how many waves pass a certain point in one second. If you could see radio waves, you could stand on the street outside your house and count them. Imagine there is a radio tower at the end of your street. The tower sends out radio signals. If you could see the radio waves, you could count how many of them pass a point in front of you in one second. A single wave from one crest to the next (or one trough to the next) is called a cycle. If five thousand waves passed the point in front of you in one second, the radio signal would have a frequency of five thousand cycles per second. You'd have to be able to count pretty fast!
Another name for cycle per second is (3) _______________________ . It is abbreviated Hz. Radio waves are used to (4) _______________________ radio and TV shows and signals for cellular (5) _______________________ , pagers, and beepers. They carry signals here on Earth and through outer space.
There are seven different types of EM. The frequency of the waves makes each type different. Frequency is the number of cycles that pass a given point in one second. The example above (where you counted radio waves from a tower) had a frequency of five thousand cycles per second. Waves in the EM spectrum that have the(6) _______________________ frequencies have the least amount of energy. Waves with the highest frequencies have the most energy. The first type we learned about is radio waves. The other six types are microwaves, infrared, visible light, ultraviolet, X rays, and gamma rays.
Microwaves are shorter waves than radio waves - shorter than 11.8 inches. The ones used in microwave ovens to cook food are about five inches long. How do microwaves cook food? When you put food into a microwave, the plate stays cool and the food gets hot. Inside food is water. Plates don't have water inside them. When the microwaves hit the food, the water inside the food begins to vibrate from the energy. Microwaves have a frequency of two billion four hundred fifty million waves per second. The water molecules vibrate with that same frequency. When molecules vibrate, they move. The movement releases heat inside the food. The heat cooks the food very quickly.
Two billion four hundred fifty million waves per second is a really big number. Scientists needed a shorter way to say it. A million cycles is a (7) _______________________ , abbreviated MHz. A thousand megahertz, or 1000 MHz, is the same as saying one billion cycles per second. The frequency of a microwave can be written as 2450 MHz. Microwaves are also used for (8) _______________________ and TV (9) _______________________ and for radar. These have shorter waves than those used for microwave ovens.(10) _______________________ (11) _______________________ microwaves can be as short as four-hundredths of an inch. When a wavelength is that short, the frequency is high - three hundred billion cycles per second. This can be written as 300 GHz, or 300 (12) _______________________ . "(13) _______________________ " means one billion.
Infrared waves are the next ones in the band of EM radiation. If you stand in the sunlight, you can feel warmth from the sun's infrared radiation. Your TV remote works on(14) _______________________ waves. When you push a button on your TV remote, a microchip in the remote starts a vibration. It produces waves in the infrared range. Infrared waves have frequencies of 100 billion to 100 trillion cycles per second. Here's another prefix to learn: "tera" means one trillion. One terahertz (THz) is one(15) _______________________ hertz or cycles per second. Since the frequencies of infrared beams are so high, the (16) _______________________ are(17) _______________________ four-hundredths of an inch to only four-hundred thousandths of an inch.
These infrared beams carry codes. Inside the TV set, another microchip identifies each code and sends a signal to raise or (18) _______________________ the volume, change channels, turn the set on or off, record a program, or do whatever you want it to do. Firefighters use infrared cameras to look through smoke and find survivors. They are used in building construction to find heating and cooling system leaks. They are also used in medicine to diagnose cancers and injuries, similar to X-rays.
Radio, microwaves, and infrared are only part of the waves that make up the EM spectrum. Read Waves and Rays, Part II to find out more.
Copyright © 2011 edHelper
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Please click this site and learn about sound waves
click to "the physics of sound"
Waves and Rays, Part II By Cindy Grigg | |
1 In Waves and Rays, Part I, you learned about radio, microwave, and infrared waves in the electromagnetic (EM) spectrum.2 Just above the infrared band of the EM spectrum is the spectrum of visible light. This part of the EM spectrum we CAN see. The waves are between 30 millionths of an inch and 14 millionths of an inch. These have very high frequencies, ranging from a hundred trillion to a thousand trillion cycles per second. Your eyes and the eyes of every creature on Earth have evolved to be able to see these particular light waves.
3 Light appears to be white to us. But by using a prism, we can separate light into its different colors. The colors are red, orange, yellow, green, blue, indigo, and violet. Each color has its own wavelength and its own frequency. You can remember the order of the colors by remembering Roy G. Biv. Each letter stands for a color in the spectrum. We see these colors in a rainbow in the sky. Sunlight passing through raindrops in the sky is refracted, or bent. When this happens, the light waves slow down. Starting with red, each color that follows has a shorter wavelength and a higher frequency than the one before it. A rainbow can only be seen in the early morning or later afternoon, when the sun is no higher than 42 degrees above the horizon.
ASSIGNMENT=Please copy the graphic organizer into your journal and complete it from the reading above in the journal
4 All the colors of the visible light spectrum combine in white light to let you see. If there's no light, you can't see color. To see, you must have light from the sun or from an electric light bulb, a fire, or another source. Everything you see has its own color. When light shines on an object, the molecules of the object absorb most of the wavelengths of the visible spectrum. When they don't absorb them, the wavelengths are reflected. If an object reflects only the red wavelengths, the object looks red to you. If the object reflects green, you see the object as green. If an object reflects all colors, you see the object as white. If an object absorbs all colors, you see it as black.
ASSIGNMENT=Please copy the graphic organizer into your journal and complete it from the reading above in the journal
5 Higher up on the EM spectrum are ultraviolet (UV) waves. These waves have higher frequency, more than one thousand trillion cycles per second, and shorter wavelength. When UV waves hit some materials that "fluoresce," or glow, they produce visible light. Special "black light" fluorescent tubes send out energy in UV wavelengths only a billionth of an inch long. Under black light, certain types of material have an eerie glow. These UV rays are what cause your skin to sunburn. A small amount of UV radiation isn't harmful to you; in fact, it allows your body to produce vitamin D that you need for strong bones. Too much UV will damage your skin. It can cause cancers, wrinkles, and early aging of the skin.
6 The next band above UV waves is X rays. Notice that the name has changed from "waves" to "rays." From here on up the spectrum, wavelengths grow smaller and frequencies become extremely high. The radiation carries large amounts of energy so they are called rays. X rays have wavelengths around one ten-billionth of an inch or more. Their frequencies are about one million trillion cycles per second. Their energy is so great that just a brief burst of them can kill diseased cells all the way inside your body. Ultraviolet waves damage the skin on the outside of your body, but X rays go much deeper.
ASSIGNMENT=Please copy the graphic organizer into your journal and complete it from the reading above in the journal
Please click this site and learn about light . http://www.gelighting.com/na/home_lighting/gela/students/science.htm
click to "these "
Please take 20 notes about what you learned from the site
7 Doctors use X rays to take pictures inside your body. You may have had an X ray taken of your teeth or of a broken bone. Having an X ray taken of a part of your body every now and then is generally safe. X ray technicians must protect themselves from X rays so that they are not exposed to too much radiation. A lead shield or an apron made of lead will not let X rays penetrate.
8 The last part of the EM spectrum is the gamma-ray band. Gamma rays are extremely high energy. They have a frequency of around one hundred million trillion cycles per second. Gamma rays are as much as ten billion times more energetic than visible light. These powerful rays are released into Earth's atmosphere when a nuclear bomb explodes and are given off by the radioactive fallout. If a gamma ray passes through a healthy human cell, it can knock electrons from some of the cell's atoms. After enough of this damage, the cell may die. That's why nuclear accidents cause radiation sickness.
What do gamma-rays show us?
If you could see gamma-rays, the night sky would look strange and unfamiliar.  The gamma-ray moon just looks like a round blob - lunar features are not visible. In high-energy gamma rays, the Moon is actually brighter than the quiet Sun. This image was taken by EGRET. |  D.J. Morris (UNH), R. Mukherjee (NASA/GSFC/USRA) |
9 Doctors use gamma rays to destroy diseased cells and make patients healthy again. Gamma rays and X rays used in radiation therapy can target the diseased cells of tumors. The tumor cells are destroyed and healthy cells can continue to grow.
10 Scientists in the last hundred years have found ways to create and use electromagnetic energy. Your everyday life is filled with EM rays that light your sight, cook your food, change channels on your TV, and entertain you. What would we do without them?
ASSIGNMENT=Please copy the graphic organizer into your journal and complete it from the reading above in the journal
11 Earth's atmosphere blocks many infrared waves, most ultraviolet waves, all X rays, and all gamma rays. There would be no life on Earth if all these high-energy waves and rays were able to get through the atmosphere.
Copyright © 2011 edHelper
Waves and Rays, Part II
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Waves and Rays, Part II FULLY EXPLAIN IN YOUR JOURNAL ASSIGNMENT=Please copy these questions into your journal and answer the questions there
Directions: Fill in each blank with the word that best completes the reading comprehension. In Waves and Rays, Part I, you learned about (1) _______________________ , microwave, and(2) _______________________ waves in the electromagnetic (EM) spectrum.Just above the infrared band of the EM spectrum is the spectrum of visible light. This part of the EM spectrum we CAN see. The waves are between 30 millionths of an inch and 14 millionths of an inch. These have very high frequencies, ranging from a hundred trillion to a thousand trillion cycles per second. Your eyes and the eyes of every creature on Earth have evolved to be able to see these particular light waves. Light appears to be white to us. But by using a prism, we can (3) _______________________ light into its different colors. The colors are red, orange, yellow, green, blue, indigo, and violet. Each color has its own wavelength and its own frequency. You can remember the order of the colors by remembering Roy G. Biv. Each letter stands for a color in the spectrum. We see these colors in a rainbow in the sky. Sunlight passing through raindrops in the sky is refracted, or bent. When this happens, the light waves slow down. Starting with red, each color that follows has a shorter wavelength and a higher frequency than the one before it. A rainbow can only be seen in the early morning or later afternoon, when the sun is no higher than 42 degrees above the horizon. All the colors of the visible light spectrum combine in white light to let you see. If there's no light, you can't see color. To see, you must have light from the sun or from an electric light bulb, a fire, or another source. Everything you see has its own color. When light shines on an object, the molecules of the object absorb most of the wavelengths of the visible spectrum. When they don't absorb them, the wavelengths are reflected. If an object reflects only the red wavelengths, the object looks red to you. If the object reflects green, you see the object as green. If an object reflects all colors, you see the object as white. If an object absorbs all colors, you see it as black. Higher up on the EM spectrum are ULTRAVIOLET RAYS. These waves have higher frequency, more than one thousand trillion cycles per second, and shorter wavelength. When UV waves hit some materials that "(4) _______________________ ," or glow, they produce visible light. Special "black light" fluorescent tubes send out energy in UV wavelengths only a (5) _______________________ of an inch long. Under black light, (6) _______________________ types of material have an eerie glow. These UV rays are what cause your skin to sunburn. A small amount of UV radiation isn't harmful to you; in fact, it allows your body to produce vitamin D that you need for strong bones. Too much UV will damage your skin. It can cause cancers, (7) _______________________ , and early aging of the skin. The next band above UV waves is X rays. Notice that the name has changed from "waves" to "rays." From here on up the spectrum, wavelengths grow smaller and frequencies become extremely high. The radiation carries large amounts of energy so they are called rays. X rays have wavelengths around one ten-billionth of an inch or more. Their frequencies are about one million trillion cycles per second. Their energy is so great that just a (8) _______________________ burst of them can kill diseased cells all the way inside your body. Ultraviolet waves damage the skin on the outside of your body, but X rays go much deeper. Doctors use X rays to take pictures inside your body. You may have had an X ray taken of your teeth or of a broken bone. Having an X ray taken of a part of your body every now and then is (9) _______________________ safe. X ray technicians must protect themselves from X rays so that they are not exposed to too much radiation. A lead shield or an apron made of lead will not let X rays penetrate. The last part of the EM spectrum is the (10) _______________________ band. Gamma rays are extremely high energy. They have a frequency of around one hundred million trillion cycles per second. Gamma rays are as much as ten (11) _______________________ times more energetic than visible light. These powerful rays are released into Earth's(12) _______________________ when a nuclear bomb explodes and are given off by the (13) _______________________ (14) _______________________ . If a gamma ray passes through a healthy human cell, it can knock electrons from some of the cell's atoms. After enough of this damage, the cell may die. That's why(15) _______________________ accidents cause radiation sickness. Doctors use gamma rays to destroy diseased cells and make patients healthy again. Gamma rays and X rays used in radiation therapy can target the diseased cells of tumors. The tumor cells are destroyed and healthy cells can continue to grow. Scientists in the last hundred years have found ways to create and use electromagnetic energy. Your everyday life is filled with EM rays that light your sight, cook your food, change channels on your TV, and entertain you. What would we do without them? Earth's atmosphere blocks many infrared waves, most (16) _______________________ waves, all X rays, and all gamma rays. There would be no life on Earth if all these high-energy waves and rays were able to get through the atmosphere. Copyright © 2011 edHelper
POST TEST - Waves and Rays, Part II
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