Use of a Light Microscope

A light microscope is a primary tool in biology that is used to view small specimens like cells.
The microscope is composed of an eyepiece (ocular lens) and objective lenses of different magnifications. The eyepiece typically magnifies x10 and the objectives can range from x4 to x100. These lenses magnify the image by focusing light.
The maximum total magnification of a light microscope is x1500 (eye piece x10 and objective lens x150 with oil immersion). However, commonly it is up to x400 magnification in a school laboratory.
Specimens are placed on a glass slide that is inserted onto the stage of the microscope. A cover slip is placed over the specimen to protect the microscope’s lens and to keep the specimen in place.
The stage is movable and allows the slide to be moved around for the purpose of viewing different parts of the specimen.
The amount of light that passes through the specimen is controlled by an iris diaphragm, located beneath the stage. More light improves visibility but may detract from contrast.
The coarse focus knob is used for approximate focusing while the fine focus knob is used for precise focusing. These knobs adjust the distance between the stage and the objective lens.
Staining using special dyes is often utilised to increase contrast and detail in the specimen. For instance, iodine stains starch in plants blue-black, and methylene blue stains the nuclei of animal cells blue.
A light microscope uses a low level of resolution, meaning it cannot distinguish the details between objects that are close together. Furthermore, it cannot view specimens at a molecular level.
Despite its limited resolution, light microscopy is still widely used because of its relatively low cost, ease of use, and the ability to view living organisms.
Care must be taken while handling and using a light microscope to avoid damage to both the user’s eyes and the instrument itself.