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. At night the dimmer button swings the low reflector into place, dimming glare from headlights behind you. During the day with the mirror tilted into the normal position, the silvered surface shows you the road behind you. The non-silvered surface, meanwhile, shows you the back seat of the car--but it's so dim you don't notice it. At night the situation is reversed. When you flip the dim button, the silvered surface tilts so it's showing you the car's ceiling, which is so dark you don't notice it. But now the non-silvered surface is showing you the road. Since the paths of sunbeams in a primary rainbow and a secondary rainbow are different, the colors of the secondary rainbow are arranged in just the reverse order of the primary one.
 * 1. How does a day /night rear view mirror work?**
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 * 2. How is a secondary rainbow formed?**
 * [][[image:rainbow3.gif width="274" height="254"]]**

The eye ball (specifically the lens at the front) is what focuses the light on to the retina at the back. When water comes into contact with the lens it changes its optical parameters. Swimming goggles stop this happening by keeping the water away from the eyes and usually, to stop any optical distortion of objects viewed, have perfectly flat surfaces through which you look.
 * 3. Why is the human vision blurred under water?**

[] Reflections of the sun found on either or both sides of the sun during sunny, winter mornings/evenings. During these times when the sun is near the horizon, the ice crystals in the air bend the sunlight, forming an image or mock of the sun on either or both sides of the sun.
 * 4. What are sundogs and how are they formed?**
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As you probably know, light has both wave and particle properties. Polarized light is a product of the wave-like nature of light. Imagine a bunch of light waves coming at you, some are oscillating up and down, others left and right and others in-between. Now imagine you put up a vertical grate (like bars on a window) that was small enough to stop the 'side to side' vibrations, but allowed the vertical ones through (kind of like if you were very skinny and could slip through the vertical bars on your jail cell, but couldn't get through them if you layed horizontally!) The light at the other side of the grate would be "polarized", ie all the light would have the same orientation (in this case, vertical).
 * 5. What does it mean to have polarized light?**


 *  [|What is polarized light? | Answerbag] [|http://www.answerbag.com/q_view/38400#ixzz1ek8qGLdV] **

That's a very good question. In the early 17th century, many scientists believed that there was no such thing as the "speed of light"; they thought light could travel any distance in no time at all. Galileo disagreed, and he came up with an experiment to measure light's velocity: he and his assistant each took a shuttered lantern, and they stood on hilltops one mile apart. Galileo flashed his lantern, and the assistant was supposed to open the shutter to his own lantern as soon as he saw Galileo's light. Galileo would then time how long it took before he saw the light from the other hilltop.
 * 6. How has the speed of light been measured in the past by Galileo?**


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 * 7. According to the legend, the Roman Fleet at Syracuse was burned when Archimedes focused the sun’s rays using a large converging mirror. Was this practical?**
 * Archimedes' mathematical proofs show both boldly original thought and a rigour meeting the highest standards of contemporary geometry. His approximation of p was not improved on until after the Middle Ages, and translations of his works were important influences on 9th-century Arab and 16th- and 17th-century European mathematicians. In his native city, Syracuse, he was known as a genius at devising siege and countersiege weapons. [[image:hw2.jpg width="371" height="145" align="right"]]**


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Blu-ray Discs contain their data relatively close to the surface (less than 0.1 mm) which combined with the smaller spot size presents a problem when the surface is scratched as data would be destroyed. To overcome this, TDK, Sony, and Panasonic each have developed a proprietary scratch resistant surface coating. HD DVD uses traditional material and has the same scratch and surface characteristics of a regular DVD. The data is at the same depth (0.6 mm) as DVD as to minimize damage from scratching. As with DVD the construction of the HD DVD allows for a second side of either HD DVD or DVD. The new discs would overlay the Blu-ray and HD DVD layers, placing them respectively 0.1 mm and 0.5 mm beneath the surface. The Blu-ray top layer would act as a two-way mirror, reflecting just enough light for a Blu-ray reader to read and an HD DVD player to ignore. Blu-ray Disc and HD DVD both support the same three video compression standards: [|MPEG-2], [|VC-1] and [|AVC] , each of which exhibits different bitrate/noise-ratio curves, visual impairments/artifacts, and encoder maturity. Initial Blu-ray Disc titles often used MPEG-2 video, which requires the highest average [|bitrate] and thus the most space, to match the picture quality of the other two video codecs. []
 * 8. How is Blue Ray different from High Definition (HD) format?****

Dual layer refers to a DVD recording technology that provides users with 8.5GB of recording space (as opposed to 4.7GB of space) on a standardDVD+R discs). Single layer DVDs, when burned, hold data on one layer on the disc. Dual layer DVDs, as their name suggests, can hold information on two different layers - this doubles how much information they can hold. There are a few different physical sizes of dual layer DVDs, all of which affect the amount of data each disc can hold. A "single sided" dual layer DVD comes in two sizes - 8cm and 12cm. The 12cm size is the standard size of a normal DVD, and can hold 8.5GB of information. The obvious benefit of using dual layer DVDs for your burning is increased size. You can hold twice the amount of data of a single layer DVD.
 * 9. What is dual layered DVD and how is it different then a regular DVD?**

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A Fresnel lens replaces the curved surface of a conventional lens with a series of concentric grooves, molded into the surface of a thin, lightweight plastic sheet. The grooves act as individual refracting surfaces, like tiny prisms when viewed in cross section, bending parallel rays in a very close approximation to a common focal length. Because the lens is thin, very little light is lost by absorption. Fresnel lenses are a compromise between efficiency and image quality. High groove density allows higher quality images, while low groove density yields better efficiency (as needed in light gathering applications). In infinite conjugate systems, the grooved side of the lens should face the longer conjugate. Explanation-A normal magnifying glass bulges out in the middle. Its curved surface bends light so that things look bigger, much as a drop of water magnifies. A Fresnel lens (pronounced “fruh-nell”) is a flat lens that magnifies. The small circular grooves on the surface are shaped like the curved sections of a normal magnifying glass. These sections bend the light in the same way as a normal lens—without needing as much material!
 * 10. What is a Fresnel lens how is it different then a regular lens?**

[] [] Fiber-optic lines are strands of optically pure **glass** as thin as a human hair that carry digital information over long distances. They are also used in medical imaging and mechanical engineering inspection. The biggest single advantage that optical fiber offers over copper wire is that of capacity, or bandwidth. With the rising popularity of the Internet, the demand for bandwidth has grown exponentially. Using a technique called wavelength ** [|division] ** multiplexing (WDM), optical networks can carry thousands of times as much data as copper-based networks.
 * 11. What is a fibre optics cable? How much data can be sent down one fibre strand?**

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