*how do you change from one objective lens to another?\n\n*from what position should you look while doing this?\n\n*which objective lens should be in place when you put the microscope away?
212771
I think the last 2 questions may refer to breakage problems. Since objectives are different lengths, switching from a shorter to a longer one could damage the slide and any part of the lens that protrudes. I guess you'd want to be off the microscope and looking at the slide and objective from the side when you change, to ensure clearance. When you stow the microscope, I'd have the shortest lens in place and the tube cranked all the way up.
505913
Make a Simple Telescope\nYou will need the following: \ntwo magnifying glasses - perhaps 1 - 1.5 inches (2.5-3 cm) diameter (it works best if one is larger than the other) \na cardboard tube - paper towel roll or gift-wrapping paper roll (it helps if it is long) \nduct tape \nscissors \na ruler, yard stick, or tape measure \nsheet of printed paper - newspaper or magazine will do \nTo assemble your telescope, do the following: \nGet the two magnifying glasses and a sheet of printed paper. \nHold one magnifying glass (the bigger one) between you and the paper. The image of the print will look blurry. \nPlace the second magnifying glass between your eye and the first magnifying glass. \nMove the second glass forward or backward until the print comes into sharp focus. You will notice that the print appears larger and upside down. \nHave a friend measure the distance between the two magnifying glasses and write the distance down. \nCut a slot in the cardboard tube near the front opening about an inch (2.5 cm) away. Do not cut all the way through the tube. The slot should be able to hold the large magnifying glass. \nCut a second slot in the tube the same distance from the first slot as your friend wrote down. This is where the second magnifying glass will go. \nPlace the two magnifying glasses in their slots (big one at front, little one at back) and tape them in with the duct tape \nLeave about 0.5 - 1 inch (1 - 2 cm) of tube behind the small magnifying glass and cut off any excess tube remaining. \nCheck to see that it works by looking at the printed page. You may have to play slightly to get the exact distances between the two glasses right so that the image comes to a focus. \nWith your telescope, you should be able to see the moon and some star clusters as well as birds, etc. \n\n+++++++++++++++++++++++\n\nMake a Simple Microscope\nYou can make a simple microscope by using magnifying glasses and paper: \nGet two magnifying glasses and a sheet of printed paper. \nHold one magnifying glass a short distance above the paper. The image of the print will look a little bit larger. \nPlace the second magnifying glass between your eye and the first magnifying glass. \nMove the second glass up or down until the print comes into sharp focus. You will notice that the print appears larger than it does in the first magnifying glass. \n\nI've included two links below for this and other info.\n\nMyst
99586
easy. For a basic refractor just reflects light through lense then bends by way of mirror into eyepiece which also has lense. Focusing lense. Hope helps.
515892
Wearing contact helps - coz ur center does not change - and has more sharp / focus than glasses.\nIf u follow eye related healthy diet/exercise - u can get by with a smaller no, like  -1.75 for starter, and help it reduce further (coz ur eye will not suffer strain from change of optical centers, etc - as is with glasses...\nTheoretically, one cannot go beyond 20/20, it is perfect vision...
24507
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.
621380
For part 1, if the cell's diameter was 1/15 of the total field, and the field was 450 microns across, then the cell's actual diameter was 450 microns/15 = 30 microns = 3 * 10^-5 meters.\n\nThe diameter of this cell in the drawing is 0.5 cm = 5*10^-3 meters.  This drawing therefore has a magnification of (5*10^-3)/(3*10^-5) = 166.6666666...times.\n\nFor part 2, The magnification is given by (size in image)/(actual size), so we have that 45000 = (1.5 mm)/a, where "a" is the actual thickness.  Solving for a, we get a = 1.5mm/45000 = 3.333*10^-8 meters = 33.3 nanometers = 0.0333 microns.\n\n-----------------------\n\nAs for the question posed in the "additional details", when the magnification of a microscope is increased, the diameter of the field being imaged decreases (choice "A").
553809
wellllllllllllllllllll a nice and easy question with an extra easy answer\n\nuse the formula \n                \n             1/f=1/u - 1/v \n\nwhere according to sign convention f,u will be negative. since it is left to the lens v=-8.2cm
253212
move your monitor slightly side way...\n\n\nas long as you still can see what your doing...\n\n\nwhether your a near sighted or farsighted... then you wont have to move backwards to stay away from direct rediation...\n\n\nheheheheh :)
187284
go to this site and look at the image:\nhttp://en.wikipedia.org/wiki/Concave_lens\n\nmake a similar experiment where 3 beams come in parallel and diverge after they come out. then imagine that the lens wasnt there, and the diverging beams all came from the same point, called the focal point. the distance from the lens to this point, which will be negative since the point is imaginary and behind the lens, is the focal length, measured in meters. if you take the reciprocal, 1 / focal length, you will get the lens power, measured in diopters
510082
Best money I EVER spent.  I also have an astigmatism.  They can still do the surgery.  Depending on where you are, see if you have a TLC (The Lasik Center) near you.  They have 'wave front' technology, which is great for astigmatism.  I had my surgery 2 years ago & it's still great.  The first couple days are a little weird, like your close up vision seems hard to focus, but that goes away.  Also, night time, there are halos for a week or two on lights, etc..  Probably the only annoying thing is that my eyes seem to be more sensitive to bright sunshine, but that's ok, I just have a really cool pair of SPY sunglasses  :)
418847
LGP depends on the area of the objective lens/mirror.  Area depends on the square of the diameter.  So take the ratio of their diameters (express them both in the same units first!) and square that ratio - that will be your answer.
593086
The Focal Length (distance from the Focal Point to the lens) is VERY different.  The Focal Point of a Telescope may be very far away.  But the Focal Point of a Microscope may be only a fraction of an inch away.\n\nAlso, the Telescope has a much larger aperature (lens diameter) to allow it to capture the tiny amount of natural light at the Focal Point.  A microscope usually illuminates the Focal Point with artificial illumination.\n\nHere's a good discussion of Focal Point and Focal Length:
549340
Mostly clarity, a well focused image across the whole field of view with well focussed crosshairs. Has he suggested a magnification? Does he want variable power? For fixed power I mostly go with 6x for hunting, higher magnification seems to make it slow to get the sight picture right and acquire the target. For variables something in the 2-7 to 4-12 range should do, 3-9 is the most popular (or was). I'd be interested to hear any alternative views on those. \n\nWaterproof and fogproof too, don't want to forget those. You need to ask if he want's glossy, matt or stainless too, it would be a shame to get him the wrong thing, if he's bothered.\n\nFor best brightness the objective diameter should be 7x the magnification, so a 4x28 gives a 7mm exit pupil, which means that the light it gives out can all be taken in through the pupil of an eye. If you have a 10x40 then the exit pupil is 4mm and only about half the pupil diameter of the human eye receives light. That's why we find funny numbers like 8x56, 6x42, 4x28 and also why a lot of sailing binoculars are 7x50. This is at the esoteric end of things though, focussed is much more important.\n\nCabelas is another Leupold stockist.
17055
Something is wrong with this question. I see it is 2 months old and would write directly if you allow email.\nI think the question should be about the object not the image. If the object is at the focal length of the lens, then the rays are parallel and easy to see with the eyes. The only image is on the inside of the eye.\nIt doesn't make sense to have length anywhere.
126479
Did you buy glasses? It sounds about like the price and description of two lenses. If your didn't buy glasses, you'd better ask them, maybe they made a mistake.
104627
Ahhhhhhh...A fledgling Amateur Astronomer!!...WONDERFUL!!\n\nThe first and foremost thing to consider is APERTURE..This is the SIZE of the opening of the telescope...The reason is, except for the moon, astro objects are dim...the larger the aperture, the more LIGHT will be gathered and focused into your eyepiece, so the clearer the image and the higher magnification you can use without blurring.\n\nYou mention a price range of $2000...That much money will buy a GREAT telescope, however, I suggest you start with a less expensive Dobsonian telescope for your first purchase.\nThis will give you some experience, HOURS of enjoyment, and will let you see if you are REALLY interested enough to upgrade to a more expensive piece. Dobsonians ( or NEWTONIAN...Same principle, REFLECTORS ) of good quality can be purchased on E-bay for around $300-$500.\n\nIn the $2000 range, look for a 'Schmitt-Cassegrain' with ' Go-To' electronics...Readily available
591682
1. make sure the specimen is actually under your field of view. then, keep adjusting the focus knobs gently until it comes into focus. also, you might want to restain your specimen.