Light vs Electron Microscopes | Electron Microscope vs Optical Microscope
Light (optical) microscope and electron microscope are two main types of microscopes. This article will discuss the functionality of those two microscopes, their similarities and finally the differences between them.
Light (Optical) Microscope
A microscope is an instrument designed to see objects, which are too small to see by the naked eye. The simplest optical microscope is the simple lens microscope, which consists only of a single biconvex lens. An object can be magnified using such a simple lens microscope. However, the magnification power is small, and the distortion of the image is high. Later, the compound microscope was developed. The traditional optical microscope has several optical elements. Namely, the mirror, microscope slide, objective lens, and eyepiece lens. The mirror, which is concave, gathers light from an outside light source and focuses the light on the sample placed on the slide. The slide is made of transparent glass. The light passes through the glass goes through the sample to the objective lens. The objective lens then refocuses the light, which is gathered by the eyepiece. The eyepiece creates an image to be observed by the eye or a camera. It must be noted that only samples, which allows light to travel through it, can be observed using such a microscope. Live samples such as bacterial cultures and fungi can be observed using such a microscope. Due to technical limitations only resolutions up to about 200 nm are possible using traditional lens systems. The effective magnification of a traditional microscope is about 2000x.
As discussed in the optical microscope, a microscope must satisfy several requirements. These requirements are an observation method, a focusing method and how the final image is produced. The observation method or analysis method used in the electron microscope is a beam of electrons. When a beam of electrons hit a certain material the beam is scattered by the material. This scattering pattern is the basis of the final image formed. The electron beam is focused using electromagnetic coils, which are analogous to the optical lenses in the optical microscope. The focused electron beam is targeted to every point of the sample to get the diffraction pattern of the whole sample. This diffraction pattern is then processed, as an optical image, to be seen by the human eye or to be studied using a computer. Since every atom will scatter the electrons, a vacuum is required to minimize the noise coming from the air molecules. Since an electron beam will obviously kill any living species, and a vacuum is required, a living sample cannot be observed using the electron microscope. The magnification of an electron microscope can be as high as 10,000,000x where the resolution is 50 pm.
What is the difference between electron microscope and light (optical) microscope?
• Electron microscope uses an electron beam, while an optical microscope uses a light beam.
• The maximum magnification of the optical microscope is about 2000x, where the maximum magnification of the electron microscope is about 10,000,000x.