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Rabb School: Graduate Professional Studies Heller School for Social Policy and Management Greater Boston Area Statistical Mechanics Meeting Graduate Student and Postdoc Resources and OpportunitiesĬurrent Diversity and Inclusion Initiatives Comparing Salmonella bacteria when using a light microscope (a), and Salmonella bacteria when using an electron microscope (b), observe the comparative increase in magnification with electron microscopy, the higher level of detail in electron microscopy, and the differences in appearance between light and electron microscopy.Summer Materials Undergraduate Research Fellowship (SMURF) Program (b) This scanning electron microscope micrograph shows Salmonella bacteria (in red) invading human cells (yellow). (b) Electron microscopes provide a much higher magnification, 100,000x, and a have a resolution of 50 picometers.Ībove: (a) These Salmonella bacteria appear as tiny purple dots when viewed with a light microscope. To see the difference in magnification and detail possible when comparing light microscopes and electron microscopes, compare the images of Salmonella (a type of bacteria) in the figure below.Ībove: (a) Most light microscopes used in a college biology labs can magnify cells up to approximately 1000 times (1000x) and have a resolution of about 200 nanometers.
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Due to the magnification limits of light microscopes, in order to gain a better understanding of cellular structure and function, scientists typically use electron microscopes (see image (b) in the figures below) that use electrons (subatomic particles) to carry images instead of light. Resolving power is the ability of a microscope to distinguish two adjacent structures as separate: the higher the resolution, the better the clarity and detail of the image. Magnification is the process of enlarging an object in appearance. Two parameters that are important in microscopy are magnification and resolving power.
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Light microscopes commonly used college classroom laboratories are used to magnify specimens up 400 times (400x), but oil immersion lenses can also be used with these microscopes for magnification of 1,000 times (1000x) to view very small structures or very small cells such as bacteria. Staining, however, usually kills the cells. Light microscopes are advantageous for viewing living organisms, but since individual cells are generally transparent, their components are not distinguishable unless they are colored with special stains (colored chemicals that makes cells appear to have color such as pink, blue, or purple). Visible light passes through the specimen and is bent through the lens system to enable the user to see the specimen. Most microscopes used in college biology laboratories are classified as light microscopes (see the figure, part (a) below) and may also be called compound microscopes since they use two lenses whose magnifications compound (multiply).
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