Microscopy comprises of the tools that are used to see/image the microscopic objects and even macromolecules. There exists a wide variety of microscopic tools for studying the biomolecules and biological processes. Light microscopy is the simplest form of microscopy. It includes all forms of microscopic methods that use electromagnetic radiation to achieve magnification. In this lecture, we shall be discussing the principles of microscopy.

Geometrical optics

Light microscopy uses glass for bending and focusing the light. Refraction (bending) of light is the manifestation of different light velocities in different materials. Refractive index of a material is therefore a measure of the velocity of light in that material. The bending caused in the light beam when it enters from one material into another is given by the Snell's law (Figure 14.1):

Figure 14.1 Snell's law

A convex lens is the simplest microscope. Figure 14.2 shows how a convex lens produces a magnified image of an object. A light ray parallel to the optical axis of the lens passes through the focus of the lens while a ray passing through the centre of the lens does not bend.

Figure 14.2 Magnification of an object by a convex lens