Microscopy

• There are two types of microscopes: light microscopes and electron microscopes.
• A light microscope uses light to illuminate the specimen, which is placed on a slide and covered with a cover slip to make it flat.
• The specimen should be thin so that light can pass through it.
• Light is shone through the specimen from below and the image is viewed through the eyepiece of the microscope.
• Sometimes a stain is used to enhance the visibility of the different parts of the specimen.
• Magnification is the size of the image divided by the actual size, indicating how much bigger it is.
• The size of the image is found by looking at the scale on the eyepiece, usually calibrated in millimeters.
• If the magnification is 400, the cells would be two millimeters divided by 400.
• A micrometer is also one millionth of a meter, denoted as µm.
• If the actual size is 0.1 millimeters and the size of the image is 20 millimeters, the magnification would be 200.
• A micrometer is one thousandth of a meter, denoted as µ or μ.
• The parts of a light microscope include the eyepiece, which is what you look in, the objective, which is usually adjustable to change the magnification, the stage on which the specimen is placed, a focusing knob that moves the stage up and down until it is in focus, and a light source, usually a light bulb underneath which shines through the specimen.
• An electron microscope fires a beam of electrons at the specimen, which pass through the specimen and are then detected by a computer, producing an image from the way the electrons have been scattered by the specimen.
• Electron micrographs are pictures taken with electron microscopes, showing a much higher magnification or better resolution than light micrographs.