Microwaves


What are they?

A microwave is a kind of high-frequency radio wave used in devicews to complete. In a mobile phone, they're made by a transmitter chip and an antenna, in a microwave oven they're made by a "magnetron".

Their wavelength is usually a couple of centimetres. Stars also give off microwaves.

external image waves3.jpg

Are they dangerous?

If you use them regularly, the fact that they are artificial, there has been growing concern that these waves can pose a significant health threat.
Prolonged exposure to microwaves is known to cause "cataracts" in your eyes, which is a clouding of the lens, preventing you from seeing clearly (if at all!) So don't make a habit of pressing your face against the microwave oven door to see if your food's ready! Recent research indicates that microwaves from mobile phones can affect parts of your brain - after all, you're holding the transmitter right by your head. Other research is inconclusive, although there is a feeling that you're more vulnerable if you're young and your brain is still growing. So the advice is to keep calls short.People who work on aircraft carrier decks wear special suits which reflect microwaves, to avoid being
"cooked" by the powerful radar units in modern military planes.
external image Health-Quality3.jpg

Where do they come from?

Microwaves are essentially high frequency radio waves, which are made by different types of transmitter. For example, in a phone, they are generated by a transmitter chip and an antenna, while in a microwave oven they are generated by a 'magnetron'.
external image cell-phone-radiation-transm.jpg

How do we detect them?

Devices called Geiger Tube - really?
external image geiger-tube.jpg

What can they be used for?

The can be used for Microwave ovens to cook food, they are used in mobile phones to send and recieve waves and satelite communication. Microwaves have wavelengths that can be measured in centimeters. The longer microwaves, those closer to a foot in length, are the waves which heat our food in a microwave oven. They are useful for transmitting information from satelites to earth, vice versa as microwave energy can penetrate haze, light rain and snow, clouds, and smoke. Smaller microwaves are used in remote sensing. These microwaves are used for radar. For example, the doppler radar used in weather forecasts. Microwaves, used for radar, are only afew inches long.
Microwaves cause water and fat molecules to vibrate, which makes the substances hot.
So we can use microwaves to cook many types of food.
Mobile phones use microwaves, as they can be generated by a small antenna, which means that the phone doesn't need to be very big. The drawback is that, being small, they can't put out much power, and they also need a line of sight to the transmitter. This means that mobile phone companies need to have many transmitter towers if they're going to attract customers.


Microwaves are also used by fixed traffic speed cameras, and for radar, which is used by aircraft, ships and weather forcasters.
The most common type of radar works by sending out bursts of microwaves, detecting the "echoes" coming back from the objects they hit, and using the time it takes for the echoes to come back to work out how far away the object is.
external image Microwave_tower_silhouette.jpgexternal image iphone-5-review-7.jpgexternal image samsung_me6104w_microwave_oven.jpg
Anything else interesting?
Microwaves cause water molecules to vibrate, how microwaves cook food is pretty simple; microwave energy is absorbed by many materials. Food contains moisture and the energy causes the moisture molecules to agitate at over two thousand million times per second. This creates heat and the food is cooked, thawed or reheated.




The Human Eye

How does it control light?
The eye uses the iris and the pupil to control how much eye enters the the visual receptors
The pupil is a whole in the center of the eye.
The irirs is the thin circular disk in the eye.
external image 30349bright-blue-eyes1.jpg
How do the eyes create an image?
Light rays reflect of a coloured object, and then its travels to the pupil, where its then refracted by the cornea, and focused by the lens, the information is then travelled to the brain through the optic nerve then an imaged is formed.


In the table below, fill the cells with very brief notes. Use the other pages to gather the information from, and you may want to go outside of this wiki if you really can't find the information here (though I'd be surprised!).



Gamma
X-rays
UV
visible
IR
microwaves
radio
How are they generated?
Gamma-rays are produced by radioactive atoms and in nuclear explosions
X-rays can be generated by machines and are naturally given off by stars and other objects. As many objects in the universe emit x-rays they are used by astronomers to detect items that could otherwise not be seen as clearly.X-rays are generated by an X-ray tube, a vacuum tube that uses a high voltage to accelerate the electrons released by a hot cathode to a high speed, they can be produced many different ways to produce different frequencies of wave that can be used to see through different objects. They are produced in parcels of energy called photons. They are also produced naturally by many objects in the universe, scientists use these to work out what far away objects are.
Powerful UV lights come from the sun, and man made things ( sun tan beds, UV lights)

William Herschel conducted an experiment measuring the difference in temperature between the colours in the visible spectrum. He placed thermometers within each color of the visible spectrum. The results showed an increase in temperature from blue to red. When he noticed an even warmer temperature measurement just beyond the red end of the visible spectrum, Herschel had discovered infrared light!
Microwaves are emitted from a number of sources, for instance, in a mobile phone, they are generated by a transmitter chip and an antenna, while in a microwave oven they are generated by a 'magnetron'. They are also released as a form of electromagnetic radiation from large stars
Naturally occurring radio waves are made by lightning, or by astronomical objects.Manmade radio waves are generated by a transmitter.
How are they detected?
Gamma-ray detectors typically contain densely packed crystal blocks. As gamma rays pass through, they collide with electrons in the crystal.
In hospitals the pictures were captured using image receptors such as thin films and photographic plates. Now they use computer technology to generate the images produced by X-Rays. Astronomers also use X-Rays, as these are absorbed by the earth's atmosphere they use balloons and satellites at very high altitudes. X-Rays can be indirectly sensed by humans but they cannot be seen by any human or animal eye.
You can use a filtrate, or a UV detector. The filtrate option is cheaper.

Our eyes cannot see infrared waves but instruments that can sense infrared energy — such as night-vision goggles or infrared cameras–allow us to "see" the infrared waves emitting from warm objects such as humans and animals.
Because humans cannot detect electromagnetic radiation we need special tools to detect them. If the waves are used for communications we use a reciver to detect them. If we are checking for contamination we can use a gieger tube to test for them.
Radio waves are detected by the use of radio telescopes.
How might they be dangerous?
Gamma rays are very harmful to living creatures.
X- rays can damage cells and cause cause cell mutation which can cause cancer or cell death. It can cause these illnesses as it produces radiation as do lots of high frequency waves, this causes cells to behave differently and can have severe effects. Ironically X-Rays are also used to treat cancer, this treatment is called radiotherapy, it involves a very high amount of radio waves. People are X-Rayed fairly regularly and although the process is safer than it used to be there is still a relatively high risk of becoming ill as a side effect of the treatment.
It can be dangerous as they damage and kill cells. When this happens to us we call it sun burn. It happens when our skin has seen a lot of sun or due to a lack of sun cream, and the skin starts to redden, it can be sore, but more often then not calms down; leaving darker, or more tanned skin. But many of the cells have been killed in the skin, for the minority this could result in cancer.

-Infrared waves are heat waves. If the cells absorb too much infrared radiation the heating will damage or kill the cells.Infrared from the sun causes sunburn
If you use them regularly, the fact that they are artificial, there has been growing concern that these waves can pose a significant health threat.
Prolonged exposure to microwaves is known to cause "cataracts" in your eyes, which is a clouding of the lens, preventing you from seeing clearly (if at all!) So don't make a habit of pressing your face against the microwave oven door to see if your food's ready! Recent research indicates that microwaves from mobile phones can affect parts of your brain - after all, you're holding the transmitter right by your head. Other research is inconclusive, although there is a feeling that you're more vulnerable if you're young and your brain is still growing. So the advice is to keep calls short.People who work on aircraft carrier decks wear special suits which reflect microwaves, to avoid being
"cooked" by the powerful radar units in modern military planes.
It is believed that exposure to large doses of radio waves can result in disorders such as cancer. There are also claims that people who are exposed to the low frequency field that are caused by overhead cables are affected.
What are the main or most significant uses?
-Doctors use gamma-ray imaging to see inside your body. The biggest gamma-ray generator of all is the Universe.-In interactions with matter, gamma rays are ionizing radiation and produce physiological effects which are not observed with any
exposure of non-ionizing radiation, such as the risk of mutations or cancer in
tissue.
-Gamma rays provide information about some of the most energetic phenomena in the universe; however, they are largely absorbed by the Earth's atmosphere. Instruments aboard high-altitude balloons and satellites missions such as the Fermi Gamma-ray Space Telescope provide our only view of the universe in gamma rays.
X- rays can be used to look at the internal structure of objects, they are often used in airport scanners as they can travel through fairly thick objects without being scattered or absorbed. This makes them very good at producing normally images of normally opaque objects, they can also be used to check for weak spots in metals. The idea of using X-Rays to see through human tissue was first formulated in 1895 in Germany. Dentists use them very often to get a more detailed image of the inside of the mouth, they can check for any chips or cavities much more easily than looking manually,especially right at the back of the mouth.
-They are used in tanning beds.
Use of tanning devices can cause skin cancer because ultraviolet goes through the skin and causes destruction to cells, causing sunburn.Because of the destructive power of ultraviolet light, it can be used to kill germs. Sunlight is a powerful disinfectant
-They are used in ultraviolet lights.
These lamps are often used to kill microbes (germs). They can be very powerful, so the people who work around them when they are turned on may need to wear protective glasses and keep their skin covered to avoid injury.

-Night vision goggles pick up the infrared light emitted by our skin and objects with heat.-A remote control uses light waves just beyond the visible spectrum of light—to change channels on your TV.-Infrared is also used for cooking in grills and toasters.
Microwaves cause water and fat molecules to vibrate, which makes the substances hot. Therefore we can use microwaves to cook many types of food. Mobile phones use microwaves, as they can be generated by a small antenna, which means that the phone doesn't need to be very big. The drawback is that, being small, they can't put out much power, and they also need a line of sight to the transmitter. Microwaves are also used by fixed traffic speed cameras, and for radar, which is used by aircraft, ships and weather forcasters. The most common type of radar works by sending out bursts of microwaves, detecting the "echoes" coming back from the objects they hit (like a bat uses echo location), and using the time it takes for the echoes to come back to work out how far away the object is. They are also used to transmit data over long distances with satelites.
-Manmade radio waves have been used for a long time to send information, receive information, and to 'see' objects. Radar uses radio waves to 'see' distant objects by bouncing waves off an object and seeing how long it takes for the waves to return. Radar can even be used to find oil or see what chemicals are in soil. Radios also use these waves to send and receive information. -Natural radio waves were first discovered in the 1930s by Karl Guthe Jansky, working for Bell Laboratories. Before his discovery, everyone thought only people could generate radio waves. Bell was detecting static on his radio channels, and had Jansky try to figure out where this static, or interference was coming from. Surprisingly, the interference was coming from space! This discovery eventually led astronomers to look at radio waves along with optical waves to find things in the sky. These radio astronomers use giant Radio telescopes, shaped like satellite dishes, to gather and analyze the waves.
-Radio waves are used for many things today. They broadcast radio and television, communicate with satellites, let mobile phones communicate with each other, make radar systems, and allow computers to share information without wires.

Good work. You put in a decent amount of effort into the microwaves section. Some formatting would need to be ironed out, but the overall effect is good.
The table is rather over-full - it needs to be memorable!

Well done!
A-

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