home

//**1. How does a day /night rear view mirror work?**// In a dimming rear view mirror you've got two reflecting surfaces--one with high reflectance, one with low. During the day you use the high reflector. At night the dimmer button swings the low reflector into place, dimming glare from headlights behind you. [|Question1] //**2. How is a secondary rainbow formed?**// Although most people will not notice it because they are not actively looking for it, a dim secondary rainbow is often present outside the primary bow. Secondary rainbows are caused by a double reflection of sunlight inside the raindrops, and appear at an angle of 50–53°. As a result of the second reflection, the colours of a secondary rainbow are inverted compared to the primary bow, with blue on the outside and red on the inside. The secondary rainbow is fainter than the primary because more light escapes from two reflections compared to one and because the rainbow itself is spread over a greater area of the sky. The dark area of unlit sky lying between the primary and secondary bows is called Alexander's band, after Alexander of Aphrodisias who first described it. [|Question2] //**3. Why is the human vision blurred under water?**// When light goes from one substance to another, it is bent around a corner, which is why lenses work. Depending on the properties of the substances, the angle of the refraction can be different. But when light from water is bent by the lens of our eyes, the light is bent differently, and the focal point of the light is so different that our eyes can't adapt to it. [|Question3]

//**4. What are sundogs and how are they formed?**// Sun dogs, or //mock suns//, are technically called solar //parhelia// (//parhelia// meaning "with the sun") and appear as bright bursts of light formed when sunlight passes through ice crystals at the proper angle. Usually, cirrus clouds in front of the sun produce sun dogs, but other ice clouds, such as ice fog and //diamond dust//, may also generate them. Sun dogs are sometimes so brilliant that dazzled observers mistake them for the sun. They are often bright white but may show a partial spectrum of color with the red wavelengths on the edge nearest the sun. Sun dogs often have comet-like appearance with a bluish-white tail facing away from the sun. [|Question4]

//**5. What does it mean to have polarized light?**// //What does the word "polarize" mean? In its usage in light and optics it means to affect light or other electromagnetic radiation in such a way that the vibrations assume a definite form. In ordinary light the vibrations are in all directions perpendicular to the path of motion of the light ray. In polarized light the vibrations can be in certain directions. Wave motion of light is a complex subject, because we can't see what is actually waving (or vibrating). It is actually the electric and magnetic fields that are waving, but these are difficult subjects also. At best we can give some simple indications of wave motion even though they don't apply so well to light and other electromagnetic radiation. Most wave motion that we can observe in nature is wave motion of matter (water waves, ocean waves, waves in a rope or spring), but light is different. It doesn't even require a medium. Light can travel in a vacuum.// //[|Question5]// //**6. How has the speed of light been measured in the past by Galileo?**// In 1667, Galileo is often credited with being the first scientist to try to determine the speed of light. His method was quite simple. He and an assistant each had lamps which could be covered and uncovered at will. Galileo would uncover his lamp, and as soon as his assistant saw the light he would uncover his. By measuring the elapsed time until Galileo saw his assistant's light and knowing how far apart the lamps were, Galileo reasoned he should be able to determine the speed of the light. His conclusion: "If not instantaneous, it is extraordinarily rapid". Most likely he used a water clock, where the amount of water that empties from a container represents the amount of time that has passed. Galileo just deduced that light travels at least ten times faster than sound. [|Question6] //**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?**// Convex lens is often called as a converging mirror as it is able to converge rays of light to a point. . It converges sunlight to a point. . Which inturn ignite the paper. //**[|Question7]**// //**8. How is Blue Ray different from High Definition (HD) format?**// So here's the technical nitty gritty before we drop the graphs n' charts on you. Both Blu-ray and HD DVD use the same kind of 405nm wavelength blue-violet laser, but their optics differ in two ways. Since the Blu-ray disc has a tighter track pitch (the single thread of data that spirals from the inside of the disc all the way out -- think: grooves on a 12-inch vinyl single vs. an Elvis Costello full-length album with 40 songs), it can hold more pits -- information -- on the same size disc as HD DVD even with a laser of the same wavelength. The differing track pitch of the Blu-ray disc makes its pickup apertures differ, however -- 0.65 for HD DVD vs. 0.85 for Blu-ray -- thus also making the two pickups technically incompatible despite using the same type of lasers. HD DVD discs also have a different surface layer (the clear plastic layer on the surface of the data -- the part that collects all your fingerprints and scratches) from Blu-ray discs. HD DVD use a 0.6 mm-thick surface layer, the same as DVD, while Blu-ray has a much smaller 0.1mm layer, which enables the laser to focus at that 0.85 aperture. [|Question8] //**9. What is dual layered DVD and how is it different then a regular DVD?**//
 * Dual-Layer DVDs**

Dual-Layer recordable DVDs come in two formats: DVD-R DL and DVD+R DL. These discs are only writable on one side of the disc, but contain two layers on that single side for writing data to. They can hold up to 8.5GB on the two layers. A DVD Burner must include support for either DVD-R DL ,DVD+R DL, or both to be able to write to the Dual-Layer discs.


 * Double-Sided DVDs**

Double-Sided recordable DVDs also come in two formats: DVD-R and DVD+R, including the rewritable DVD-RW and DVD+RW. Double-Sided discs include a single layer on each side of the disc that data can be recorded to. These discs can hold about 8.75GB of data if you burn to both sides. DVD Burners that support DVD+/-R/RW discs can burn to Double-Sided discs, all you have to do is burn to one side, flip the disc like an old LP record, and burn to the other side [|Question9] //**10. What is a Fresnel lens how is it different then a regular lens?**// The basic idea behind a Fresnel lens is simple. Imagine taking a plastic magnifying glass lens and slicing it into a hundred **concentric rings** (like the rings of a tree). Each ring is slightly thinner than the next and focuses the light toward the center. Now take each ring, modify it so that it's flat on one side, and make it the same thickness as the others. To retain the rings' ability to focus the light toward the center, the **angle** of each ring's angled face will be different. Now if you stack all the rings back together, you have a Fresnel lens. You can make the lens extremely large if you like. Large Fresnel lenses are often used as ­solar concentrators. [|Question10]