Intro: Operating Procedure Of Compound Light Microscope System in 10 Steps

Microscope is a tool that enables us to view things that are too small to be seen with the naked eye. 

The most common type of microscope used in school science laboratories is the

compound light microscope. It uses a system of two or more lenses to collect and focus

transmitted visible light through a specimen to the eye. 

It is the principle tool for the study of biology and is often referred to as bright field microscopy. Animal cells, plant cells, protozoa and bacteria can be easily seen with a compound light microscope. The typical compound light microscope is able to magnify from 40x to 1000x, increasing our ability to see detail so that

objects as small as 0.2 micrometres (µm) or 200 nanometres (nm) can be seen. 

Compound light microscopes may be monocular (for viewing using only one eye) or binocular (for viewing using both eyes). 

Compound light microscopes from various manufacturers may appear different but operate on similar principles. A microscope is a delicate precision instrument and

care must always be used when using, transporting and maintaining it.

A typical school microscope has three magnifications: Scanning, Low and High. Each objective and eyepiece (ocular lens) will have the magnification written on it. Some microscopes will also have an oil immersion objective.

The total magnification is the ocular magnification multiplied by the objective magnification.

See table below

Operating procedure

To Set up and use a compound light microscope obey the following rules to achieve good result

1. Read and be familiar with the user manual for your model of microscope.

2. Carry the microscope with two hands, one under the base and the other gripping the arm or frame.

3. Gently place the microscope on a flat, level surface and plug into a power source. Some microscopes have a built in light source but others have a mirror to focus natural light or an external light source.

4. With a built-in light source, turn on the light source and adjust the light setting so that it is not too bright by turning or sliding the brightness adjustment knob on the base.

5. ‘If using an external light source directs the light via the mirror. Rotate the low power objective into position. Remove the eyepiece, look down the body tube and adjust the mirror and diaphragm setting so light is reflected up the tube and a circle of evenly illuminated light is visible in the field of view. Replace the eyepiece. Use the concave mirror side if the microscope has a fixed condenser lens or the flat mirror side if the microscope has an adjustable condenser’ 1.

6. The iris diaphragm is located just above the light source on the bottom side of the stage.

Using the lever attached, you can increase or decrease the amount of light reaching the test sample. Look through the eyepiece and adjust the sub-stage iris diaphragm to allow sufficient comfortable light through.

7. Between the stage and the iris diaphragm is the condenser. The condenser further aids in the focusing of the light onto the specimen. In some microscopes it can be moved up and down. To begin with, position it close to the stage. If you have a problem focusing your specimen then adjust the position of the condenser.

8. Adjust the stage down as low as possible with the coarse focus knob.

9. Begin by viewing the specimen with the lowest power objective lens in place and then increase to the higher power objective lenses.

10. Select the 4x scanning objective by rotating the nosepiece, ensuring it clicks into place

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