Why are telescope mirrors made of glass?
473094
Glass is more dimensionally stable - it doesn't expand or contract when the temperature changes - and it can be polished to a very smooth surface.   The finish is a very very thin layer of metal.\n\nRead "The Perfect Machine" by Ronald Florence if you want to learn more.
268357
option 4. coz a telescope helps us see images of gigantic objects, so a diminished image wrt object forms. also, the final image formed is upside down(though it is virtual) coz the ist image formed is real and inverted.\ntrust me, i just gave my phyics board exams.
60088
Glass is made up of mostly silica sand.  In order for the sand to become glass, it must be heated up to a super-hot tempature of 1,982°C/3.600°F.\nUsually white sand is preferred when making glass, because of lower concentrations of iron, which turns the glass a greenish color.\nSometimes lead is added to sand to make a softer type of glass with exceptional clearity.  Max. lead content can only be 33%.  It is more complex to work with, but easier to cut.\n\nTwo natural glasses that occur are: obsidian, a natural by-product of volcanic eruptions; also, fulgrites, which are formed when lightning strikes sand or rocks, super-heating then cooling, forming glass.
832073
Glass is made of sandstone.  Stone would be earth.
508036
Glasses and contacts operate on the same basic principles, but contacts have to accomplish the same thing in a much smaller space (for obvious reasons).  Contacts are often made out of more bendable materials, for comfort.  Since they are closer to the eye than glasses, they are also more curved.  I suspect that the materials used in contacts may have a higher index of refraction than glass, since they're not as thick, but I don't know if that's true or not - just conjecture on my part.
780624
Use of a fresnel lens, a lens made up of circular rings that focus the light to the small area of reflecting mirror. This in turn projects the image to the screen. \n\nTake the optic workings of a telescope or microscope:\n\nOptics - microscopes and telescopes all invert the image because if they didnt, it would mean that another lens had to be added, increasing money cost. A lens is convex on both sides. That means the middle is thicker than the edges. A microscope or telescope has two lenses (basically).\nThe objective lens (usually larger and closer to the specimen or object) which allows the image of the object to be reduced to a smaller workable image inside the scope. \nThis image is inverted inside the scope. It is also too small to see with the eye, so you need another lens, the eyepiece. The eyepiece focus's your eye on the image and magnifies \nit so you can see it. Every lens has a focal length, the point at which the image is formed away from the surface of the lens. \n\nOk now we take this to the overhead:\n\nSame principle but in different Direction. You manipulate the object, transparency, over the light source after the light is passed thru the fresnel. The fresnel forms the smaller inverted image on the mirror. It is then reflected to the screen where the focal length is adjusted (moved closer or farther away from the screen )
62786
made using easy-to-find materials. The components of this telescope are: \n\n\nring to secure the eyepiece lens from behind \nring for centering the eyepiece lens \neyepiece: lens with focal length of 20-50 mm. You can buy one in an optical or photographic shop, or you can get one free by using the lens of a disposable camera. \nring to secure the eyepiece lens from the front \na cardboard tube for the eyepiece. You can use the tube from a roll of plastic food wrap or paper towels. You can also use short sections of this tube to make rings 1, 2, and 4 which you need to hold the eyepiece lens in place \ncoupling between the eyepiece tube and the main tube. This is a hollow cylinder with an outer diameter that fits snugly into the end of the main tube and an inner diameter that provides a snug but movable fit to the outside of the eyepiece tube. You can make the coupling using several plywood disks glued together or using a polystyrene cylinder with a hole bored through it. If you use polystyrene, you will need to add an opaque covering at each end. \nmain tube. Use a cardboard or plastic tube about as long as the focal length of the objective lens and with an outside diameter of 50-60 mm about. Suitable sources include map mailing tubes and core tubes for carpets, drawing paper, or wrapping paper. \nobjective lens. You can use a common eyeglass lens with a focal length of 500-1000 mm. You can buy it in a optical shop. Ask the optician to reduce the lens diameter in order to fit it precisely into the tube cap \ndiaphragm. Cut it from a black card, then open a hole of about 15 mm in diameter in the center of the disk \nCap of the tube. If you buy a tube for drawing sheets, you should have a cap which will be useful for retaining the objective and the diaphragm. Otherwise, you can made it with a disk of cardboard. Make a series of radial cuts around the edge of the disk to make a set of tabs, Moisten the tabs; then place the tube cap on one end of the principal tube and bend the tabs around the outside of the tube. Glue the tabs together where they overlap, but be careful not to glue the cap to the principal tube yet. When the glue is dry, slip the cap off and cut in the cap a hole a few mm less in diameter than the outside diameter of principal tube. \nThe distance between objective and eyepiece lenses must be equal to the sum of their focal lengths. The eyepiece tube must stick out a few centimeters so you can move it to focus the telescope. Make the length of the principal tube short enough to allow you to grip the protruding part of the eyepiece tube with your fingers as you adjust the focus.\nThe eyepiece tube must slide smoothly in its channel, but it should not be loose enough to fall out if you hold the telescope vertically. Paint the inside of the tubes with black opaque paint (matte finish) or India ink . Secure the cap of the main tube to keep it from pulling away from the tube.
672330
Glass is made from silica and sand, heated at very high temperatures.  Different colors come from adding different metals and other elements.
65373
Optics - microscopes and telescopes all invert the image because if they didnt, it would mean that another lens had to be added, increasing money cost. A lens is convex on both sides. That means the middle is thicker than the edges. A microscope or telescope has two lenses (basically).\nThe objective lens (usually larger and closer to the specimen or object) which allows the image of the object to be reduced to a smaller workable image inside the scope. This image is inverted inside the scope. It is also too small to see with the eye, so you need another lens, the eyepiece.  The eyepiece focus's your eye on the image and magifies it so you can see it. Every lens has a focal length, the point at which the image is formed away from the surface of the lens.
417677
For refractors, the most common problem is chromatic aberration. In this, you get little rainbows around bright objects and a blurrier image around others. This happens because the lenses act like prisms. All refractors are subject to this, but some *very* expensive ones have it less. They fix this by using more than one type of glass.\n\nFor reflectors, the main problem is spherical aberration. This is caused by the mirror not being a perfect paraboloid. It is much easier to grind a sphere than a paraboloid, and most mirrors are first ground to a spherical shape. If the subsequent grinding isn't done right, the resulting images will be blurrier than need be. For decent images, the mirror's shape has to be within 1/4 of a wavelength of light, and for a good image it should be correct to within 1/10 of a wavelength. Considering how small the wavelength of visible light is, you can see how hard that is.
730887
I have a pair of those interesting deep-dish-shaped double-domed parabolic mirrors from Edmund Scientific, the top one sits upside-down on the bottom one, and the top one has a hole in it.  So when you put something inside it, and move away at an angle, an image of the object appears to be sitting above the top dish.  I ask people, "Hand me that little pink pig sitting on that dish".  They see it, reach for it, pick up nothing, reach for it again, and see their fingers apparently pass right through a solid object.\n\nWhat is the reality there?  My eyes tell me there's a little pink plastic pig sitting on the top of that dish.  Yet when I try to pick it up, my fingers pass right through it.  But then I distort the mirrors a little, and the pig blurs in an odd way that lets me see that he's actually a reflected image from inside the unit.  And if I understand optics sufficiently, I understand that it is possible, with certain arrangments of parabolic mirrors, to erect "real" images (versus the more common "virtual" images that we see in most mirrors and lens) of objects, and even design and build versions of my own, with the effects and capabilities fully determinable in advance.  That's reality.\n\nReality does exist.  Granted, we have a limited and distorted view of it due to the limitations of our senses, but it does exist.  For example, this desk in front of me seems like a solid object.  But in truth, my view of it is limited by the fact that my eyes are not able to resolve the electrons orbiting the nuclei that make up the desk, and that the vast majority of this desk is vacuum, therefore the fact that, when I touch this supposedly-solid desk, what's actually happening is that the electrostatic field generated by the electrons of the desk are exerting a force against the electrostatic field of the electrons orbiting the nuclei of the atoms making up my fingers.  There are no "solids" touching anything, just fields pushing against each other the way 2 magnets can push against each other.\n\nTo me it looks like reality begins immediately outside your eyes.  All is reality.  The only place it ends is inside your head, when you misinterpret what your limited senses tell you.
770421
No one really knows. Galileo is generally credited with making one and using it specifically for astronomy but he was not the first to make one.\n\n"The first telescopes may have been Assyrian crystal lenses[1], but the Visby lenses tentatively suggest that the technology was known to the Arabs and Persians. Leonard Digges is sometimes credited with the invention in England in the 1570s, but usually credit for assembling the first telescope is given to an unknown Dutch spectacle maker in about 1608. Some name that person as Hans Lippershey (c. 1570 – c. 1619), but Jacob Metius and Zacharias Jansen also claimed to have invented a telescope during the same period. Even if Lippershey did not make the first one, he publicized it. Galileo Galilei made his own telescope in 1609, calling it at first a "perspicillum," and then using the terms "telescopium" in Latin and "telescopio" in Italian (from which the English word derives). Galileo is generally credited with being the first to use a telescope for astronomical purposes"
50232
glass. cheaper ones are made of plastic. usually comes set in a metal ring with a handle attached.
906783
Good question. The colour of a mirror can be affected by the colout of the glass and the colour of the reflective backing. In most mirrors the glass is clear and the backing is silver so they are nominally silver in colour.\n\nOf course this becomes somewhat comlicated when something becomes reflected in them.
111328
Silicon is typically the main ingredient in glass however different elements and compounds are added to color glass or make it stronger.  Windows with high R values are filled with an inert gas such as Argon in beween two plates to increase energy efficiency.  The case protecting the Declaration of Independence and other important US documents are also filled with argon.
409995
There are two basic kinds, refracting telescopes and refleting telescopes. Refracting telescopes depend on light bending through transparent materials (glass). Have you ever put a pencil in a glass of water? Try it. See how it seems to bend? That's because the light travels at a different (slower) speed through the water, which makes it bend. \n\nA telescope lens is circular, so that all the light rays refract in the same direction, focusing to a point, and the image appears larger (closer.)\n\nThe reflecting telescope works differently. It has a curved mirror to reflect all the light rays to a point. So more light is gathered, across the area of the mirror. You see an image that is larger (closer.)
421431
Well if you are talkin about a mirror made of floated glass a layman can c the quality of it other wise ind. know how is required i think (i am not proffesional in it, just being in a float glass plant for a week). If it is a mirror and you c a distracted reflection then b sure that there is impurity in the glass, as well as the transparency of float glass is supposed to be very high compares to the conventional one.