Investigating cells with a light microscope

Once slides have been prepared, they can be examined under a microscope.

Aims of the experiment

• To use a light microscope to examine animal or plant cells.
• To make observations and draw scale diagrams of cells.

Method

Rotate

Rotate the objective lenses so that the low power, eg x10, is in line with the stage.

Focus

Turn the coarse focus so that the stage is as close to the objective lens as possible. You should not look through the microscope to do this.

Place the slide

Place the microscope slide – either one you have prepared, or a permanent slide – on the stage. Line it up so that the specimen – if you can see it – is in the centre of the stage, where the light passes through.

Focus

Focus the slide towards you by turning the coarse focus adjustment.

Record an image

Draw a low power image or record a digital image of what you see. Then, rotate the objectives so that the high power objective, eg x40, is in line with the stage.

Re-focus

Bring the slide back into focus using the fine focus adjustment. If you do not succeed, go back to low power and re-focus, then try again.

Risks

• Care must be taken when looking down the microscope if the illumination is too bright.
• Care must be taken when using microscope stains.
• Care must be taken when handling coverslips and microscope slides.

Drawing the image

Record the microscope images using labelled diagrams or produce digital images.

When first examining cells or tissues with low power, draw an image at this stage, even if going on to examine the slide with high power.

A low power diagram is used:

• as a plan to show the arrangement of any distinct regions of the tissue, for example the tissues in a plant root
• to show the outline of individual cells that make up the tissue, if the tissue is uniform

A high power diagram is then produced – a detailed image of a part of the slide. It is usually drawn to show a single cell, eg of a single cheek cell or onion cell.

Make sure that microscope drawings are fully labelled