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Electromagnetic waves have unique traits
EQ: How are em waves different from mechanical waves?
|An electromagnetic wave is a disturbance | |
|True or false for the next three.. | |
|Mechanical waves transfer energy through a vacuum. |False |
|A wave is a disturbance that transfers energy. |True |
|Most EM waves are invisible but detectable. |3. True |
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|What are we surrounded by every moment? | |
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|Can we feel the waves in our bodies? |Waves |
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| |Sometimes but most of the waves are invisible to us |
|Can we see the waves? | |
| |No |
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|When do we perceive EM waves presence? |When we use our eyes to see or feel the heat of the sun |
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| |Radios, TVs, cell phones |
|What are some devices that require the use of em waves? | |
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| |A disturbance that transfers energy through the vibration of |
|Define electromagnetic waves. |electric and magnetic fields |
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| |EM waves have the same properties of wavelength, speed, amplitude|
|Are em waves the same as mechanical waves? |and frequency. Unlike mechanical waves, EM waves can travel |
| |through a vacuum |
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| |An area around an object where the object can apply a force, a |
| |push or pull, to another object without touching it. |
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| |Electrically charged particles |
|Define field. | |
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|What causes an electromagnetic wave? | |
|How EM Waves Form | |
|When do em waves occur? |When electrically charged particles that cause a disturbance or |
| |vibration in an electric or magnetic fields |
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| |Electrically charged particles that exert a force on one another |
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| |Electrically charged particles that exert a force on one another |
| |magnetically |
|Define electric field. | |
| |The particles can start a disturbance or vibration in their |
| |electric or magnetic fields |
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|What causes a magnetic field? | |
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| |Perpendicular, or at right angles to each other |
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|What happens when an electrically charged particle moves quickly?|From trough to trough or crest to crest |
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|What is the geometrical relationship between the magnetic and the|The wavelengths would be farther apart. The crests and troughs |
|electrical fields? |would be farther apart. |
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|How is the wavelength of the wave measured? | |
| |Magnetic and electric |
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| |EM waves form when the moving charged particles transfer energy |
|How would a diagram of a wave with a lower frequency differ from |through a field. |
|the one below? |Mechanical waves form when energy is transferred to particles of |
| |matter in a material medium. |
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|What two types of fields make up an EM Wave? | |
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|How do em waves and mechanical waves differ in the way they form?| |
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|Sources of EM Waves | |
|What are two sources of em waves on earth? |the sun |
| |technology |
|Where does most of the earth’s energy come from? | |
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| |the sun |
|Electromagnetic Waves and Vacuums | |
|Define radiation in terms of EM waves? |The transfer of energy in the form of an EM wave |
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| |No |
|Is it the same as the heat transfer of a mechanical wave? | |
| |A mechanical wave vibrates the particles in a medium and as the |
|How does a mechanical wave radiate? |energy travels through the medium the energy is reduced |
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| |An EM wave can travel without a medium |
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| |No |
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|How does an em wave differ in radiation? |Yes, as long as it does not bump into something or get absorbed |
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|Does it lose energy as it travels? | |
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|Can EM waves travel forever? | |
|How em waves travel in a vacuum | |
|How can em waves travel great distances? |They do not give up energy as they travel |
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| |No. They need a medium to travel and space is a near vacuum |
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|Can sound waves travel through space? Why or why not? |150 million km or 93 million miles |
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|How far do the sun’s rays travel to reach earth? | |
| |All directions |
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|What direction do em waves travel? |Seismic Waves |
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|What other type of wave travels in this direction? | |
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|As the distance from the source of an em wave increases, the |Decreases |
|waves energy _______. | |
| |Because the farther they are from their source the more they |
|Why? |spread out and so there are fewer waves in a given area and thus |
| |less energy |
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|Speed of an EM Wave | |
|How fast does an EM wave travel? |300,000 km per second or 186,000 miles per second |
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| |7 |
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|How many times can an em wave circle the earth in 1 second? | |
| |8 minutes |
|How long does it take for the sun’s rays to reach our planet? | |
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|How are EM waves used to measure distances in space? |By the time it takes an EM wave to travel at the speed of light |
| |from one place to another |
|EM Waves and material matter | |
|What are four things that can happen when an em wave interacts |transfer energy |
|with matter? |reflect |
| |refract |
| |4.defract |
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| |Its direction changes |
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|What happens when an em wave encounters a material medium? | |
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|What happens to the energy in the em wave when it changes | |
|direction? |Direction of the energy changes |
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|Transferring Energy | |
|What two ways do mechanical waves transfer energy? |potential |
| |kinetic |
|In what form do EM waves transfer energy in a vacuum? | |
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| |1. moving potential energy from one place to another |
|Energy Conversion | |
|What two things does the interaction of an EM wave and a medium |type of wave |
|depend upon? |nature of the material |
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|What type of em wave does a microwave use? |microwaves |
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|Describe the four steps needed for a microwave oven to cook a |device on the oven produces microwaves and sends them to a |
|potato. |reflecting fan |
| |microwaves are reflected in many directions by the blades of the |
| |fan and then again by the sides of the oven |
| |Microwaves move through the air without transferring energy to |
| |the air. |
| |Microwaves transfer energy to the water molecules inside the |
| |potato in the form of heat, cooking the potato |
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| |Reflection causes waves to strike food from many directions so |
| |it cooks evenly |
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|How does a microwave cooking depend on reflection? | |
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