Microscopes & drawing labelled diagrams

Why are microscopes used?

To observe subcellular structures of a microorganism

How do you use a light microscope safely?

• Always start with the lowest power objective under the eyepiece

• Clip the slide securely on the stage

• Adjust the light source (mirror) so that light goes up through the stage

• Use the coarse focusing wheel to focus on the slide

• Move the middle so that the cell you will draw is in the middle of the view

• If needed, move a higher power objective into position above the slide

• Use the fine focusing wheel to bring the cell back into focus

What precaution is needed if you use the Sun as a source of light?

Making sure the microscope mirror does not point directly at the Sun as this could permanently damage your eyesight

Why must you never use the coarse focusing wheel with a higher objective?

It may crash into the slide

If you cannot see the part of the slide you need with a higher power objective, what must you do?

Go back to using the lower power objective to bring it back to centre view and to focus it before returning to the higher power objective

What apparatus is used to draw a labelled diagram of a plant cell?

• Light microscope

• Unlined paper

• Sharp HB pencil

• Rubber

• Ruler

What is the method to drawing a labelled diagram of a plant cell?

• Focus the microscope on a single cell

• Carefully draw details of the parts that are important to your study (other parts can be drawn just in outline)

• Keep looking back at the specimen as you make the drawing

• Only draw what you see, not what you think you ought to see

What must you give your labelled diagram?

A clear title saying what the specimen is and the magnification

What are some important things to remember when drawing the plant cell?

• Keep the relative sizes of structures approximately correct

• Label all the key parts of your drawing

• Labels should be outside the drawing and label lines must not cross

• Use a ruler to draw label lines to link labels to the correct parts of the drawing

• Never use shading