Microscopy - Types of Microscopes

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to scan a specimen that 's usually tagged with fluorescent dyes. • When the laser hits the dyes it causes them to give off fluorescent light. These microscopes can be used to look at different depths in thick Specimens. O It can be used to observe whole living specimens, as well as cells. The images are high resolution and show high contrast. Multiple images produced by the microscope can be combined by the computer to generate 3D images of a specimen. O 9 TYPES OF ELECTRON MICROSCOPES There are two types: TRANSMISSION ELECTRON MICROSCOPE (TEM) 。 O • Use electromagnets to focus a beam of electrons, which is then transmitted through the specimen to produce 20 images. Denser parts of the specimen absorb more electrons, which makes them look darker on the electron micrograph. 。 。 •The electrons form a 2D black-and-white image • The specimen has to be chemically fixed by being dehydrated and stained. • The specimens to be viewed need to be very thin, and stained with heavy metals. High magnification and resolution SCANNING ELECTRON MICROSCOPES (SEM) • High resolution and 3D imaging SEMS scan a beam of electrons across the specimen O Electrons bounce off the surface of the specimen to create an n image. The images produced show the surface of the specimen and can be 3D but they give lower resolution images than TEMS.. The images are black and white. 0 · O ELECTRON MICROSCOPE Advantages ♥ Electron microscopes can have a 2000x better resolution. than light microscope. • Higher magnification D than light microscopes. Disadvantages • The interior of an election. microscope is a vocuum. We cannot view living specimens... Electron microscopy requires very. careful staining and the specimen. often has to be very thin. Electron microscopy can lead to artefacts (false images). Large, not portable and very expensive Specimens, even whole ones for use in SEMS, have to be dead, as they are viewed while in a vacuum. The metallic salt stains. used for staining specimens may be potentially hazardous to the user.