Use of a Light Microscope

A light microscope uses light and lenses to enlarge an image of an object.
A microscope consists of the following parts: eyepiece, objective lens, stage, light source, and focus knobs.
The eyepiece (ocular lens) is where you view the image. The standard eyepiece magnifies the image 10 times (x10).
The objective lens provides further magnification. Typically, microscopes have multiple objective lenses (x4, x10, x40) that can be rotated into place.
The stage is where you place the slide with your sample.
The light source is below the stage and provides the light which will pass through your sample.
The focus knobs allow you to move the objective lens closer or further from the stage to fine-tune the focus of your image.
To use a light microscope, start with the lowest power objective lens. Place your slide on the stage and use the focus knob to sharpen the image.
Rotate to the higher power lenses to see more details. Always focus with the low power lens first and then only fine-tune the focus on higher powers.
Light microscopes can magnify objects up to 2000 times, but most school microscopes magnify up to 400 times.
In terms of cells, a light microscope can show cell walls, nuclei, and cytoplasm in plant and animal cells. You will not be able to see smaller components like mitochondria.
Specimens must be thin and often dyed to increase contrast between the different components.
Remember that the image you see is 2D and the cells are in fact 3D structures.
A limitation of light microscopes is that they can’t show smaller cells and internal structures as clearly as electron microscopes. Nonetheless, they are a valuable tool for initial analysis and are more readily available in school laboratories.