Required practical 1: using a light microscopeSpec 4.1.1.2
- Place a thin piece of tissue (for example onion epidermis, or cheek cells) on a clean microscope slide. Add a drop of water or a stain such as iodine solution.
- Lower a cover slip onto the specimen at an angle, using a mounting needle, so that no air bubbles are trapped.
- Clip the slide onto the stage. Select the lowest-power objective lens and turn the coarse focusing knob until the specimen is roughly in focus.
- Use the fine focusing knob to get a sharp image. Then switch to a higher-power objective lens and refocus with the fine focusing knob only.
- Draw what you see using a sharp pencil. Use clear, unbroken lines, no shading, and make the drawing large. Draw only a few cells accurately rather than many badly.
- Label the sub-cellular structures with straight label lines that do not cross. Add a title and the magnification.
To find the total magnification of a light microscope, multiply the magnification of the eyepiece lens by the magnification of the objective lens. The magnification of your drawing is found with the equation magnification = size of image ÷ size of real object, using the width of your drawing and the real width of the cell.
Safety: carry the microscope with two hands, handle glass slides and cover slips carefully, and take care with the stain, which can mark skin and clothes. Start with the lowest-power lens so that the objective lens does not hit the slide.