1. MICROSCOPES

2. Microscopes reveal the world of the cell: • Advances in science often coincide with advances in tools and technology • Use of the microscope led to development of the cell theory: - All living things are made of cells - cells come from other cells by reproduction.

3. Terms: Magnification: the increase in the apparent size of an object Resolution: a measure of the clarity of an image (The ability of an optical instrument to show two close objects as separate)

4. Types of microscopes: • Light microscope: works by passing visible lightthrough the specimen - Glass lenses bend light to magnify the image - Light microscopes can effectively magnify images only about 1,000 times

5. The light microscope

6. 2. Electron microscope: uses a beam of electrons instead of light Advantage: much greater resolutionandmagnification Disadvantage: preparing the specimen kills the cells

7. There are 2 types of electron microscopes: Transmission electron microscope:(TEM) used to study details of internal cell structure • Specimens are cut into extremely thin sections and stained with atoms of heavy metals • A beam of electrons is aimed throughthe slice

11. Scanning electron microscope:(SEM) examines the cell surface after it has been coated with a thin layer of metal