Microscopes Aim To be able to use a microscope draw a scientific diagram of an onion cell.
Context Microscopes can be used in Biology, Chemistry and Physics. They are used to look at cells, bacteria, crystal shapes and to find faults in structures.
Risk Assessment Risk: Hazard: Control Measure:
Equipment Label a diagram of the microscope neatly and clearly. Ensure the work has your name on.
Diagram arm - attaches the eyepiece and body tube to the base. base - supports the microscope. body tube - tube that supports the eyepiece. coarse focus adjustment - a knob that makes large adjustments to the focus. diaphragm - an adjustable opening under the stage, allowing different amounts of light onto the stage. eyepiece - where you place your eye. fine focus adjustment - a knob that makes small adjustments to the focus (it is often smaller than the coarse focus knob). high-power objective - a large lens with high magnifying power. low-power objective - a small lens with low magnifying power. mirror (or light source) - directs light upwards onto the slide. revolving nosepiece - rotating device that holds the objectives (lenses). stage - platform on which a slide is placed. stage clips - metal clips that hold a slide securely onto the stage.
Method: Making a Temporary Slide
Cut through an onion and take off on leaf of a bulb.
Using a pair of forceps peel off the inner layer (the epidermis). Make sure you only get the see-through layer.
With a pipette put a drop of water on a clean microscope slide.
Put the epidermis on top of the drop of water. Make sure it is flat and there aren’t any air bubbles.
Put a cover slip on top of the epidermis and water droplet.
Put one drop of iodine on one side of the coverslip. This will let you see the cells.
Put the cut edge of a piece of filter paper on the other side of the coverslip and watch the iodine being drawn through.
Put the slide under the microscope
Method: Using a Microscope
Put the microscope is on low power (the shortest objective lens should be in line with the stage).
Secure the slide to the stage with the object in the centre of the stage where the light will be able to pass through it and in line with the objective.
Turn the coarse focus knob so the objective is as close to the slide as possible.
Focus away from the slide until the object is in focus.
Turn the revolving turret head until the high power objective is in line with the stage.
Using the fine focus knob until the image of the object is sharp.
If you can’t get a sharp image go back to low power and restart at step 1.
Use a pencil
No shading (dotting only)
Use a ruler to draw label lines
Theory: Parts of the Cell Aim To be able to label the parts of the cell that you can see. Some Key Words Mitochondria Chloroplast Vacuole Cytoplasm Nucleus Cell Membrane Cell wall
Analysis and Evaluation Aim To be able to explain what our results show and evaluate our experiment.
Analysis My diagram is of a… The organelles in my diagram are… The job of each organelle is… The organelles found in plant and animal cells are… I could see the organelles because…
Evaluation My experiment went… I had problems with … because… My classmates had difficulty with… To improve my experiment I could… My results would be more reliable if I…