Biology report on microscopes.

A SEM Scanning Electron Microscope works differently to a TEM microscope. A sharply focused electron beam moves over the sample to create a magnified image of the surface. Some electrons in the beam scatter off the subject and are collected and counted by an electronic device. Each scanned point on the sample corresponds to a pixel on a television monitor, the more electrons the counting device detects the brighter the pixel on the monitor is. As the electron beam scans over the entire sample, a complete image is displayed on the monitor. SEMs are particularly useful because they can produce three-dimensional images of the surface of objects. A SEM microscope and magnify and image up to 100,000 times.

How do light and electron microscopes differ?

The obvious reason being the way they work; one with light and one with electrons, however the electrons are shot from the top and you do not look down a lens rather than having the light shot up from the bottom and looking down a lens. The magnifying power of each microscope is massively different, the light microscope has 1000x that of the naked eye however the TEM electron microscope has 1,000,000x and the SEM electron microscope has 100,000x. The price is also substantially different, the light microscope being around £500-£1000 and the electron microscopes the best ones being upto £5,000,000

How does a light microscope work?

Light is shone or reflected from underneath a glass slide with the subject is placed between two thin pieces of glass. The image of the object is magnified by lenses in the body of the microscope and the observer sees the image through an eye-piece.

By Owain Taylor