lab exam 1

• Light microscopes use light rays passing through lenses to magnify the object.
• The stereomicroscope (dissecting microscope) is designed to study entire objects in three dimensions at low magnification.
• Compound light microscopes are used for examining small or thinly sliced sections of objects under higher magnification that that of the stereomicroscope.
• Compound refers to the use of two sets of lenses: the ocular lenses located near the eye and the objective lenses located near the object.
• To improve contrast, the microscopist uses stains or dyes to bind to cellular structures and absorb light.
• Photomicrographs, also called light micrographs, are images produced by a compound light microscope.
• The transmission electron microscope is analogous to the compound light microscope. The object is ultra-thinly sliced and treated with heavy metal salts to inprove contrast.
• The scanning electron microscope is analogous to the dissecting light microscope. It gives an image of the surface and dimensions of an object.
• The electron microscope has greater resolving power.
• Resolution is the minimum distance between two objects at which they can be seen as two seperate objects.
• The use of high-energy electrons rather than light gives electron microscopes a much greater resolving power.