Senin, 25 Januari 2010

Light as Wave.

What is light?

Light is electromagnetic radiation, particularly radiation of a wavelength that is visible to the human eye. In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether it is visible or not.

In the seventeenth and eighteenth centuries, scientist debated about lights, did light travel as particle or as a wave.

Light as a particle

Albert Einstein showed by imagining photoelectric effect, when light interacts with an object, it forms a particle.

Light as a wave

Thomas Young formed an experiment called double-slit experiment.

Single beam of laser light passes through the slits, then it’s diffracted so it spreads to the screen.


In double slit experiment, we determine λ using this equation

λ= ax / D

a, is the separation of the slits
x, is the distance between the centers of the fringes
D, is the distance between slits to the screen

Sabtu, 23 Januari 2010


"The Wave"

How many of you have "waved" or gave some other sign of acknowledgment to passing riders, only to have nothing happen in return? Are you offended or insulted by this? Do you "attain happiness" when a passing rider returns your gesture? Do you not wave at all, or is this mannerism completely irrelevant when riding a motorcycle? This topic almost borders on the question: "What is the meaning of life?" and my sense is that it may have the same philosophical ramifications.
Let me start by stating up front that the majority of my research was gathered from on-line "riders" on one of the more popular electronic Motorcycle Forums, which will remain anonymous in respect for those who responded, and, for the fact that I neglected to state "up front" in my message that I was researching material for this article. For all you aspiring free-lance writers, this is an electronic on-line and ethics "no-no" and the head "SysOp" (Manager of the Material, On-Line Big Brother, Keeper of the Text, etc.), quickly reminded me of this. They also tend to discourage "surveys and other opinion polls" when they appear on-line. I agree with this position 100%, and I learned a valuable lesson for future reference on being clear of my intents when asking questions on-line.
I apologize in advance for all those respondents who were not aware of this, when I asked the question: "What is your opinion on waving to other MC riders when you are passing them on your bike? I am just curious as to what your feelings are regarding this informal gesture?"
Well, I did not expect the number and the variety of responses I received! Talk about opening Pandora's Box! I mean, do other rider really care? Personally, I have waved, and not waved, depending on the immediate situation at the time. I have seen "big-rig" tractor-trailer drivers wave at one another, and on certain occasions, I have seen vintage car and hot-rod owners wave at one another, and especially if they are attending a rally or a run. I can't remember however, when was the last time I saw two Chevy Caprice or Ford Bronco owners salute each other when passing.
Two common themes were evident in many of the responses. The first is when riding in the city, or in heavy traffic, it's acceptable not to wave if you are too busy watching traffic and/or using the clutch. The second is waving is generally accepted protocol to passing riders only when it is convenient and safe, and that usually means "on the open road. That's understandable and sounds reasonable to me.
Most people said they wave to all bikes, regardless of brand, whether they get acknowledged or not, and that's my credo, especially on the open road, 500-plus miles from home. I recall in 1990, on the road during the 50th Anniversary at Sturgis, a small group of us were on some pretty desolate highways in Wyoming. Anyone who has ridden up there knows why they call it: "Big Sky Country..." I remember going through small towns out on the plains where there were only two establishments to be seen: the church and the tavern! I was "more than happy" to pass other riders on some of the longest and loneliest stretches of highway imaginable. As far as I recalled, we were happy to seen other human beings on those roads. I remember thinking, boy, if one of us breaks down here, we're hosed!! On that trip, 1300-plus miles from home, you gladly waved to all riders, and they in turn, always waved back.
There were more than a few responses that said Harley riders tend to wave only to other Harley riders. Another set of responses stated that the "sport bike crowd" or "crotch-rocket riders" tend to wave "only to their own kind." Then, I received a few folks that said they would only wave if the other rider waves first." Another rider informed me that in the United Kingdom, a "nod" is much more acceptable than a "wave," (leave it to our stodgy, British brothers). In reality, this is because British enthusiasts ride with their left hand "on the near-side."
The most interesting response was from a guy who said that once a "platoon" of Harley riders gave him the "clenched fist salute" in unison as they passed. Obviously, that group had been watching the McLaughlin Drill Team too many times. Then there was the guy on the Sportster who "elbowed" his female passenger when she waved to another rider on a Japanese bike. Now that guy needs some therapy! So what were the statistics for this little, informal sampling? The results are fairly simple:
· Always wave 74%
· Wave only when it is safe 22%
· Nod or other gesture 4%
So, when the results were tallied, everyone does something to acknowledge the other rider, and I think this is a good thing. One person summarized this whole question by stating: "I've met some nice people and found some great roads, just because of a wave." After all, isn't this one of the benefits of riding motorcycles? Today, motorcycle technology has advanced to the point, where one rarely sees another rider "broke down" on the side of the road, with the exception of an occasional flat tire. Think about that next time you wave to a passing rider. In time of need, the person you waved to may be the only one who stops to help you.
In its simplest form, I guess it boils down to camaraderie of the saddle, and personal pride to say to the other rider: "Hey, this is a great sport and I am having fun... how about you?"
For myself, I will always wave to the other rider, and always when it's safe to do so, for in that, we all share the spirit of the open highway. Until next time, ride safe, and I'll see you on the road.

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Physics: How Microwave Works?

All About Microwave:

How does a Microwave Work ?
The microwave oven consists of a magnetron tube, which converts electricity into high frequency microwaves. Microwaves are a form of electromagnetic energy, like light waves or radio waves, and occupy a part of the electromagnetic spectrum. Microwaves cause food molecules to vibrate rapidly, creating friction that produces heat which then cooks the food. In other words, food cooked in a microwave simply absorbs microwave and turns their energy into thermal energy, which cooks the food. Microwaves are colourless, odourless, tasteless, and these are not radioactive.
Microwave oven is one of the most energy efficient appliances money can buy today. For example, it takes 18 times the electricity to bake a potato in a regular oven than in a microwave. Microwaves cook from the outside towards the center of the food.
Microwave ovens are faster for most cooking jobs because the energy heats the food and not the oven or the containers. They don't also heat up the kitchen, especially in the summer time like the other cooking appliances.
When was microwave first used to cook food ?Microwaves were used during World War II as the basis for radars to detect and locate enemy aircrafts at long distances. During this time (ie) in 1945, it was accidentally discovered by an American engineer Percy Le Baron Spencer who was working with radar equipment and noticed that some candy he had in his pocket had melted. Spencer realized that it was these microwaves that had heated the candy and his body too ! He worked for Raytheon at that time, and they soon realized the potential of this discovery, and produced the first household microwave oven.
Can microwaves hurt you ?A small amount of microwaves won't hurt you. Microwaves are anyways present all around us, in the form of satellite transmissions, cellular telephones, and even by the thermal radiation from our surroundings. A properly constructed microwave does not leak any microwaves.
Why can't I use a metal container in a microwave ?Microwaves causes currents to flow in metals, these currents may heat the metal hot enough to cause a fire. Therefore, it is not a good idea to use metal containers in a microwave.
Time required to boil 8 ounces of room temperature (about 75F) water:
The higher the wattage of the microwave the faster the microwave cooks.
850 - 1000 watts - takes less than 2 minutes650 - 850 watts - takes 2 - 3 minutes or less400 - 650 watts - takes 3 - 4 minutes or less
Microwave tips to remember:
Do not use metal pots and pans, or metal utensils.
Food is completely cooked if the bottom of plate feels warm in the center.
Cook small foods, under 2 inches in diameter, for less time, since the heat penetrates more quickly from all sides.
To prevent food from drying out, cover the food with a vented cover whenever cooking or re-heating.
Always use less salt and seasoning than normal when cooking in the microwave, since this draws out the moisture and will toughen the food. Add the salt later in the cooking process.
Use less water when microwaving, due to the shorter cooking time.
Stir liquids periodically when microwaving, and stir the outer sections, which cook faster, into the center of the dish and center sections to the outside. This equalizes the temperature throughout the food.
Cook dense food for more time in the microwave, since dence food cooks slower than porous food.
Arrange food with thickest parts, and bulky vegetables on outside of plate and quick-to-heat less-dense foods in the center. Spread a single serving of a main dish in an even layer on plate.
Turn large food over occasionally in the microwave, for more even cooking.
Microwave cooked food require some standing time, since they continue to cook for a few minutes after they are removed from the microwave oven. Cover this food with plate, waxed paper or paper towel to direct the heat back into the food.
Make sure not to block the vents of the microwave oven, or the oven will overheat

History of Microwave

The microwave oven did not come about as a result of someone trying to find a better, faster way to cook. During World War II, two scientists invented the magnetron, a tube that produces microwaves. Installing magnetrons in Britain’s radar system, the microwaves were able to spot Nazi warplanes on their way to bomb the British Isles.
By accident, several years later, it was discovered that microwaves also cook food. Called the Radar Range, the first microwave oven to go on the market was roughly as large and heavy as a refrigerator.The idea of using microwave energy to cook food was accidentally discovered by Percy LeBaron Spencer of the Raytheon Company when he found that radar waves had melted a candy bar in his pocket. Experiments showed that microwave heating could raise the internal temperature of many foods far more rapidly than a conventional oven. Microwave OvenThe first Raytheon commercial microwave oven was the 1161 Radarange, which was marketed in 1954. Rated at 1600 watts, it was so large and expensive that it was practical only for restaurant and institutional use.
In 1967, Amana, a division of Raytheon, introduced its domestic Radarange microwave oven, marking the beginning of the use of microwave ovens in home kitchens. Although sales were slow during the first few years, partially due to the oven’s relatively expensive price tag, the concept of quick microwave cooking had arrived. In succeeding years, Litton and a number of other companies joined the countertop microwave oven market. By the end of 1971, the price of countertop units began to decrease and their capabilities were expanded.
All electromagnetic energy can be characterized as waves with a specific wavelength and frequency distributed over a continuous range known as the electromagnetic spectrum. For example, some radio waves have a wavelength of 6 feet (12 meters) and a frequency of 50 million hertz (Hz-cycles per second). Visible light waves have a wavelength of 400 to 700 millimicrons, and typical X-rays have a length of 0.01 millimicrons and a frequency of 30 x 10¹² millions.
Microwaves (short waves or high frequency radio waves) are the shortest of radio waves, with a length of 0.1 millimeter and a frequency of 3 x 109 Hz. They are found in the non-ionizing portion of the energy spectrum, between radio waves and visible light. "Non-ionizing" means that microwaves do not detach charged particles and produce atoms with an unbalanced plus or minus charge. Microwaves can therefore safely produce heat and not cause food to become radioactive.
Microwaves are reflected from most metals but they produce inductive resonance's in the atoms of many other substances. It was the discovery of their reaction to metals that led to the invention of radar. It was their ability to produce resonant coupling that led to the invention of the microwave oven.

How to use it

In microwave cooking, the radio waves penetrate the food and excite water and fat molecules pretty much evenly throughout the food. No heat has to migrate toward the interior by conduction. There is heat everywhere all at once because the molecules are all excited together. There are limits, of course. Radio waves penetrate unevenly in thick pieces of food (they don't make it all the way to the middle), and there are also "hot spots" caused by wave interference, but you get the idea. The whole heating process is different because you are "exciting atoms" rather than "conducting heat."
In a microwave oven, the air in the oven is at room temperature, so there is no way to form a crust. That is why microwavable pastries sometimes come with a little sleeve made out of foil and cardboard. You put the food in the sleeve and then microwave it. The sleeve reacts to microwave energy by becoming very hot. This exterior heat lets the crust become crispy as it would in a conventional oven.

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Great Powers, Comes With Great Responsibility