Start off...
We study lenses and mirrors in our tour so far. However, you
may also not so clearly notice that many of the common instruments that we use today
depends entirely on the mechanism of lenses and mirrors. In this section, you will once
again discover for yourself instruments and how they harness the greatness of lenses and
mirrors.
The Microscope
This is an
optical instrument used to increase the apparent size of an object. A magnifying glass
using ordinary double convex lens which has a short focal length is a simple microscope.
When an object is placed nearer such a lens than its principal focus, for example, when
within its focal length, an image is produced that is larger than the original object.
The two lenses used are named as Objective(the lens nearer to the object) and Eyepiece(the
lens nearer to the eye of the observer) When an object is in focus, an inverted image is
formed by the lower lens at the point inside the focus of the upper lens. This image then
serves as an object for the upper lens, which produces another image larger still but
still realistic and visible to the eye of the observer.
The Compound Microscope
The compound microscope which is invented in the early 17th
century, consists of two or more such lenses(convex lenses) fixed in the two ends of a
hollow metal cylinder and the cylinder is then mounted upright on a screw device, and this
allows the cylinder to be raised or lowered above the object to be magnified until a clear
magnified image is formed.
It is commonly used in bacteriology(the study of bacteria),
biology, and medicine in the examination of such extremely minute objects such as
bacteria, unicellular organisms, and plant and animal cells and tissue. Technology has
permitted us to make use of different types of light to enhance the magnification , and
resolution of the object.
In summary, the microscope uses lenses as follows ;
(1) Objective, one lens forms an object of the viewed object .
(2) Next, the eyepiece another set of lens magnifies the image
