The microscope, sometimes called the compound
microscope, has two short focal length convex lenses. The objective gives a real, inverted
image of the object which is then magnified by the eye lens, giving a final virtual image. In
many professional microscopes both the eye lens and the objective lens are made of two or
more lenses fitted together.
In a microscope the object is slightly further from the
objective lens than its focal length. Shorter focal length objectives give higher magnifications
and this means that the object will be very close to the objective lens.
Some
microscopes even have oil between the lens and the object to help give high quality
magnification.
The final image is usually at a distance of about 25 cm from the eye,
if it was closer than this you would get eye strain if you tried to use the microscope for a long
time.
With normal microscopes you can get magnifications up to about 500 times but
using an electron microscope, that works in a quite different way, it is possible to magnify
objects by over 100 000 times!
