what are the pros and cons to light microscope objective lenses?
370114
they are cheap compare to electron microscope.\nbut there is limitation of zooming large.
703298
For a convex lens, a thinner lens will have a greater focal length because the length is mostly determined by the curvature of the lens.  Greater curvature gives shorter focal length.  A thin lens is almost flat, therefore doesn't have as much curvature.  Light striking the lens at a greater angle(more curvature) will refract more.
744055
I tried multi focal and they are really difficult to get used to.  I went back to mono, its easier  to change spectacles than keep moving your head around to keep the image focused in the "sweet spot" in the multis....:D
243026
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.
134550
They are a vast improvement over bifocals, which give you a line across your vision, once you get over playing "find the focus," rolling your head up and down.  I am used to them now, except that it is still counter-intuitive to move something away from my eyes to see it better.  But when that gets too frustrating (as in trying to thread a needle), I do what I always have done; take may glasses off.  I must say, though, that being beyond the age when I can get 20/20 in both eyes with correction has its drawbacks.  Then there is the problem of taking your glasses off to wipe the smudges off, only to discover the "smudges" are inside your eye!\n\n"What a drag it is getting old."  Mick Jagger (who should know by now!)
978537
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.
635627
How about a polarized lens
828006
It's a great toy. A 60mm aperture (2.4") won't gather much light (which also determines the amount of detail you can make out at higher magnifications). Is this a refractor? Cheap models suffer from various distortions produced by inferior coatings, poor collimation, etc.\n\nYou can see a long way (moon, mars, stars, etc), but thre real question is how good the image is (fuzzy, dim, etc)\n\nTry the following website (page goes to a celestron 760 mm refractor - a decent instrument. Lots of description.)\n\nhttp://www.telescope.com/jump.jsp?itemID=116608&itemType=PRODUCT&path=1%2C2%2C4%2C13&KickerID=699&KICKER
485221
Yes.  A diverging lens "demagnifies"  It makes objects smaller rather than larger.  These are used for people who can't see far off.
428587
Depending on the kind of lens - diverging or converging - it either concentrates light on a point (converging), or its sends light out as if it _came_ from a focal point on the other side.\n\nfor more information, look here:\nhttp://en.wikipedia.org/wiki/Optics
254369
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
406370
More light is needed as the magnification is increased since the size of the hole of the objective lens decreases. Try it!
615134
glasses-pros- don't have to stick fingers in eyes, don't dry out, no risk for infection,\nglasses-cons-not always attractive, can leave red intents on bridge of nose if not properly fitted or slightly heavy, can break easily, dangerous if you get hit in the face, unless you pay an arm and a leg you risk annoying scratches on surface of lense and issue of sun when outside, though they do have perscription sun glasses or the clips, maintenance, when first start wearing have the issues of motion sickness until used to them, cost, can't wear them to sleep, can't see when wake up\ncontacts-pros-don't have to worry if they match what you are wearing, can sometimes help filter allergens from eyes (sometimes, not always!!!)\ncons-risk of infections, not good for dry eyes, must remember to follow drs instructions and lense manufatcturer's recommendations.  though following those directions will eliminate much of the risks of infections. can tear if not cared for properly. cost, not recommended that you sleep in them so can't see when first wake up
160744
I suspect that the focal length would change sign.  That is, a convex lens would now act like a concave lens and vise versa.
546123
The lens elements are made of transparent materials. Glass is the most widely used material due to its good optical properties and resistance to scratching. Various plastics, such as acrylic (or PMMA), the material of Plexiglas, can also be used. Plastics allow the manufacture of strongly aspherical lens elements which are difficult or impossible to manufacture in glass, and which simplify or improve lens manufacture and performance. Plastics are not used for the outermost elements of all but the cheapest lenses as they scratch easily. Moulded plastic lenses have been used for the cheapest disposable cameras for many years, and have acquired a bad reputation: manufacturers of quality optics tend to use euphemisms such as "optical resin".
48322
Getting the objective lens wet is usually not a problem - especially if you take the trouble to clean it with a special lens-cleaning tissue.\n\nMany things you look at through a microscope are wet preparations, that is the specimen is mounted in a drop of water or stain (to make certain structures visible). The cover slip holds the liquid in place and stops the liquid from evaporating too quickly. Evaporation can be quite quick because of the heat from the illuminating lights.\nWet preparations are esential if you want to view living tissue or water creatures.\n\nA dry mount is usually a dead specimen mounted in a special glue which also sticks a cover slip in place. The cover slip in this case serves to protect the specimen since these slides are usually made for collections.\n\nIn my experience the cover slip can help to protect the specimen in wet preparations when an inexperienced user rams the objective lens down onto the specimen!
1114621
The poster just above mine provided the correct reason for why it is used, but they failed to say when.  On many microscopes today, there are 4 different settings; low (red), medium (yellow), high (blue), and oil immersion (usually represented with a white ring).  For the low, medium and high settings, you do not need to use the oil.  However, in order to see clearly on the highest, you would need to use the oil.\n\nIt might be opposite with the red and blue rings, I don't have a microscope in front of me at the moment.