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Showing posts with label Wave. Show all posts
Showing posts with label Wave. Show all posts
Sunday, January 11
Waves in a Ripple Tank: A Virtual Activity

Waves in a Ripple Tank: A Virtual Activity
Go to the site http://www.falstad.com/ripple/. A “Ripple Tank Applet” window will open that runs a simulation of waves generated in a ripple tank.
By “clicking on” any or all of the three task bars in the upper right hand corner of the applet window, you can change the type and number of wave sources. The third task bar allows you to use the mouse to edit the waves or walls (barriers). You can adjust the speed, resolution, frequency, brightness, and/or damping of the wave simulation to obtain a clearer representation of the wave phenomena. A complete and detailed set of directions for how to use this simulation is linked to the web page.
Your task is to use this web site to identify and investigate various wave properties and characteristics. You will hand in pictorial representations of…
Circular Wave
long wavelength
shorter wavelength
Plane Wave
long wavelength
shorter wavelength
Reflection
Plane Wave Off Angled Straight Barrier
Plane Wave Off Concave (Parabolic) Barrier
Circular Wave Off Straight Barrier
Diffraction
Plane Wave Around a Barrier
Plane Wave Through an Opening
Circular Wave Around a Barrier
Circular Wave Through an Opening
Refraction of a Plane Wave
Refraction due to Temperature Gradient (simulates sound wave over lake)
Interference
Two Circular Waves (wide spacing between sources)
Two Circular Waves (closer spacing between sources)
One Plane and One Circular Wave (this is a tricky one to simulate!)
Single Slit (plane wave)
Double Slit (plane wave)
Triple Slit (plane wave)
Doppler Effect
Beats
Something else you find really interesting
You have two options for completing this assignment:
· Make small (about 4 in. x 4 in.) sketches with colored pens/pencils…OR…
· Use a “screen capture” program to copy and paste the actual images from the applet window into a document (MS Word with text boxes, for example), which can then be saved and printed.
You can download a free trial version of an easy to use screen capture program at http://www.etrusoft.com/. The image shown on this handout was “captured” using this program.
Another option is to use the “print screen” function on the keyboard and then paste the picture in your report. Pressing “print screen” (Prnt Scrn) on the keyboard copies the entire screen, so you may want to enlarge the ripple tank window to fill the entire screen.
You can probably fit 6 diagrams/sketches on each side of a page. Be sure to label each sketch.
Go to the site http://www.falstad.com/ripple/. A “Ripple Tank Applet” window will open that runs a simulation of waves generated in a ripple tank.
By “clicking on” any or all of the three task bars in the upper right hand corner of the applet window, you can change the type and number of wave sources. The third task bar allows you to use the mouse to edit the waves or walls (barriers). You can adjust the speed, resolution, frequency, brightness, and/or damping of the wave simulation to obtain a clearer representation of the wave phenomena. A complete and detailed set of directions for how to use this simulation is linked to the web page.
Your task is to use this web site to identify and investigate various wave properties and characteristics. You will hand in pictorial representations of…
Circular Wave
long wavelength
shorter wavelength
Plane Wave
long wavelength
shorter wavelength
Reflection
Plane Wave Off Angled Straight Barrier
Plane Wave Off Concave (Parabolic) Barrier
Circular Wave Off Straight Barrier
Diffraction
Plane Wave Around a Barrier
Plane Wave Through an Opening
Circular Wave Around a Barrier
Circular Wave Through an Opening
Refraction of a Plane Wave
Refraction due to Temperature Gradient (simulates sound wave over lake)
Interference
Two Circular Waves (wide spacing between sources)
Two Circular Waves (closer spacing between sources)
One Plane and One Circular Wave (this is a tricky one to simulate!)
Single Slit (plane wave)
Double Slit (plane wave)
Triple Slit (plane wave)
Doppler Effect
Beats
Something else you find really interesting
You have two options for completing this assignment:
· Make small (about 4 in. x 4 in.) sketches with colored pens/pencils…OR…
· Use a “screen capture” program to copy and paste the actual images from the applet window into a document (MS Word with text boxes, for example), which can then be saved and printed.
You can download a free trial version of an easy to use screen capture program at http://www.etrusoft.com/. The image shown on this handout was “captured” using this program.
Another option is to use the “print screen” function on the keyboard and then paste the picture in your report. Pressing “print screen” (Prnt Scrn) on the keyboard copies the entire screen, so you may want to enlarge the ripple tank window to fill the entire screen.
You can probably fit 6 diagrams/sketches on each side of a page. Be sure to label each sketch.
Labels:
PEKA,
Physics Activity,
Physics Help,
Physics Note,
Physics SPM,
Wave
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Wednesday, November 26
The Oceans' Wave Power
For more than 200 years inventors worldwide have filed patents for wave-power technology of a dazzling variety of designs-bobbing objects ("ducks"), buoys, articulated rafts, floating bags, overspills, and many others. There has been no shortage of ideas. Many of these ideas are in fact technically feasible, so it seems a shame that this renewable energy resource has not been much used. The main challenge is building a system that is economically attractive when so many other forms of energy production (nuclear, fossil fuels) receive subsidies and already have infrastructure in place. There are some wave power systems in place around the globe: the Faroe Islands; Islay, Scotland; Oahu, Hawaii (providing power for the U.S. Marine Corps. base there); Santo, Spain; Portugal; and even the world's first commercial "wave farm" in England.
The World Energy Council has estimated that wave power could produce as much energy in a year as 2,000 oil, gas, coal and nuclear power plants' twice the amount of electricity produced worldwide-by generating as much as 2 terawatts (that's 1 trillion watts).
Not every place is a candidate for wave power generation. Prime locations identified are Scotland, northern Canada, southern Africa, and the Atlantic Northeast and Pacific Northwest of the United States. Experts have estimated that wave-power systems in the Pacific Northwest alone could generate up to 70 kW per meter of coastline.
Typical Designs
Wave-power systems can be located onshore or offshore, and come in a surprising range of designs. There are currently four basic "capture" methods: point absorbers (largely vertical, with a relatively small footprint on the surface); attenuators (horizontal footprint, arranged parallel to the waves to undulate with the flow); terminators (perpendicular to the waves); and overtopping (perpendicular to the waves, which break over the system). There are different power take-off systems including hydraulic ram (water hammer pumps water above the starting point); elastomeric hose pump (peristaltic, like your intestinal tract), pump-to-shore, hydroelectric turbine, air turbine, and linear electrical generator. Here are some systems already in operation, or close to it:
OFFSHORE: POINT ABSORBER SYSTEMS
1. The Salter "Duck"-In 1970 Stephen Salter ("the father of wave power"), a professor at the University of Edinburgh, designed a wave-power device that could both stop 90 percent of the wave motion and convert 90 percent of that into electricity, a standard that all other designed continue to be measured against. Ironically, the Duck itself never went into use. During the 1990s, a project based on the Duck and dubbed the OSPREY (Ocean Swell Powered Renewable Energy), commenced in the Clyde Estuary of the Scottish coast. Capable of generating 1 mW of power, the OSPREY was on its way to becoming an unqualified success until Hurricane Felix came along and sunk it (at great expense in terms of both money and confidence).
2. The AquaBuOY wave energy device-AquaBuOYs (Finivera Renewables) really do look like navigational buoys, and this is no coincidence. Obviously, maximum output from a wave-power device should be during those times when the waves are at their highest, but if the technology can't withstand rough seas (as with the OSPREY, above), they aren't much good. Operating on the premise that since navigational buoys can survive for decades in all sorts of conditions, the AquaBuOYs were designed to ride the waves for an estimated 100 years. The vertical wave action drives a two-stroke hose pump that directs pressurized seawater into a turbine connected to a generator; the resulting power is sent via an underwater transmission line. While at least four projects are in the permitting process (including one in Makah Bay, WA), as of this writing.
3. PowerBuoy "Like the AquaBuOY above, the PowerBuoy resembles a navigational buoy, although one with long cylinder extending far below that houses the mechanics of the system. These PowerBuoys (Ocean Power Technologies) are placed from one to five miles offshore in 100 to 200 feet of water, and can be ganged together to form a "wave-power farm" such as the one to be installed off the coast of Santo, Spain. That 1.39MW station will have one 40kW and nine 150kW PowerBuoys.
OFFSHORE: ATTENUATOR SYSTEMS
1. Pelamis - Ocean Power Delivery, Ltd., developed world's first commercial offshore wave-power facility using its Pelamis Wave Energy Converter, a string of steel cyclinders hinged to articulate. It lies half-submerged, like a 150-meter-long, bright red sea snake (pelamis is the genus for the sea snake), more or less facing into the waves. The cylinders contain hydraulic pumps activated by the wave action; the electricity comes as high-pressure oil gets pumped into generators. The first phase of the wave farm, located 5 km off the coast of Portugal, comprises three 750kW Pelamis "snakes" that combined to generate 2.25 MW; another 28 are expected to be added, bringing the total power generated to 22.5 MW'enough to provide electricity for more than 15,000 homes.
OFFSHORE: TERMINATOR SYSTEMS
1. Nearshore OWC-This is an offshore version of the Limpet, described below.- OFFSHORE: OVERTOPPING SYSTEMS
1. Wave Dragon-Overtopping systems work very much like hydroelectric dams, using the potential energy of water stored at an elevation higher than the turbines it drives. The Wave Dragon overtopping system funnels the waves into its own reservoir to create a head; the water is then released through channels that contain turbines. The Wave Dragon is moored 25 to 40 meters offshore in deep water, somewhat like a floating beach.
ONSHORE: OSCILLATING WATER COLUMN:
1. Limpet (Land Installed Marine Powered Energy Transformer)- This an oscillating water column (OWC) system to convert the waves' kinetic energy to electrical power. Picture a box with the open end submerged but slightly tilted toward the incoming waves, with air trapped inside the box. Now imagine there is a narrow outlet for this air, and inside this tube is a turbine. As the waves raise the level of the water inside the box, the air rushing in and out of the tube powers the turbine. A Limpet system (WaveGen) in Islay, Scotland, uses an inclined oscillating water column (OWC) system optimized for the area's anverage annial wave intensity, and feeds a pair of 250kW generators. The Limpet power station in the Faroes is very similar. WaveGen also designs a near-shore oscillating water-column system.
There are many companies designing wave-power systems using these and other designs (such as the tapered channel system, an onshore system, and the pedulor system, an offshore device), and new ones seem to come along frequently as more countries come to recognize the potential of wave power.
Wave Power Advantages
1. Wave energy is an abundant and renewable resource. 2. Even though not every country has coastline, the combined potential output of wave-power generation would meet all the electricity needs of the world. 3. Although the equipment represents a substantial investment, the "fuel" is free and not confined by geopolitical boundaries. 4. The effect on the environment is deemed to be minimal.
Wave Power Disadvantages
1. These are most effective near coastlines, of which there is a finite supply. 2. Large scale systems are still in the early stages.
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Labels:
Energy,
Power,
Wave
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Thursday, September 18
High and Low Sounds
THE PITCH OF A SOUND means how low or high it is. In a music band,
the bass drum's deep boom is low-pitched, while the triangle's shrill tinkle is high-pitched. Pitch depends on how many times the sound source moves to and fro, or vibrates, each second. This
is the same as the frequency - how many sound waves are produced each second. The frequency of a wave is measured in units called Hertz, Hz. For example, the note of middle C, in the
middle of a piano keyboard, has a frequency of 261 Hz. Frequency is related to wavelength, since higher frequencies have shorter waves. The length of a middle C sound wave is 126 centimetres.
the bass drum's deep boom is low-pitched, while the triangle's shrill tinkle is high-pitched. Pitch depends on how many times the sound source moves to and fro, or vibrates, each second. This
is the same as the frequency - how many sound waves are produced each second. The frequency of a wave is measured in units called Hertz, Hz. For example, the note of middle C, in the
middle of a piano keyboard, has a frequency of 261 Hz. Frequency is related to wavelength, since higher frequencies have shorter waves. The length of a middle C sound wave is 126 centimetres.
What sounds can we hear?
We hear many sound frequencies, from the shrill notes of bird song to the deep growl of traffic. But, because of the way our ears work, we do not hear all of the sounds around us. Our ears pick up frequencies from about 20 to 20,000 Hz (Hertz, vibrations per second). We hear sounds below 80 Hz as low, deep booms, thuds or rumbles. Frequencies below about 30 Hz may not be heard clearly, but if they are powerful enough, we can feel them as vibrations in the air and ground. Our ears are most sensitive in the range from 400 to 4,000 Hz. (Human speech tends to be around 300-1,000 Hz.) Sounds above about 5,000 Hz are extremely high-pitched squeaks, hisses and screeches. As people get older, their ears become less sensitive to high notes. So a young person can hear a bat's very high-pitched squeaks, while an older person cannot.
Labels:
Wave
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Monday, September 15
Telecom network
A mobile phone sends and receives messages by radio waves. The radio waves travel to and from a tranceiver (transmitter/receiver) station which connect the call into the standard telephone network. Countries are divided up into different areas, called cells, and each cell has its own tranceiver station. In an areas where a lot of people live, there are many small cells because there likely to be many people using mobile phones. In sparsely populated areas populated areas, the cells are larger.
Inside a mobile phone
A "mobile" is a low-power radio transmitter-receiver. It has mouthpiece to change sound waves into electrical signals (like a microphone), and an earpiece to change electrical signals into sound waves (like a loudspeaker). The transmitter-receiver only needs to send and pick up waves from the nearest cell tower, which is usually just a few kilometres away. However hulls or tall buildings may block the radio signals. also, in areas where the cell towers are farther apart, the signals may be too weak to travel to and from the phone.
Inside a mobile phone
A "mobile" is a low-power radio transmitter-receiver. It has mouthpiece to change sound waves into electrical signals (like a microphone), and an earpiece to change electrical signals into sound waves (like a loudspeaker). The transmitter-receiver only needs to send and pick up waves from the nearest cell tower, which is usually just a few kilometres away. However hulls or tall buildings may block the radio signals. also, in areas where the cell towers are farther apart, the signals may be too weak to travel to and from the phone.
Labels:
Wave
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