The light microscope visualises objects or details which are invisible to the eye, which does not have sufficient resolution to see them.
The light microscope uses light. It has two lenses:
The resolution of light microscopes is up to 0.2 micrometres and is limited by diffraction of light. There are methods available that come close to this limit by using an immersion lens (in oil) or by reducing the light wavelength (although this is restricted to the visible spectrum).
The light microscope can visualise the individual cells of living objects (bacteria, yeasts, unicellular organisms) or fixed objects (tissue sections). It is also used to study the physics of materials and in geology.
The objects become very clear under the illumination although the tissues often need to be stained in order to examine them. As not all tissues take up the stain in the same way these staining techniques can also be used to distinguish specific objects or to differentiate between two similar organisms (Gram staining for bacteria).
The Gram stain can distinguish between the two main types of bacteria (Gram positive and Gram negative). The rods are Bacillus anthracisbacteria. The other cells belong to the immune system. © DR