Imaging Biological Samples with Optical Microscopy

Optical microscopes use light sources to illuminate samples. The light passes through a series of lenses; the condenser focuses the light on the sample, while the objective and ocular lenses create a magnified and inverted two-dimensional image.

The numerical aperture of a lens determines its ability to gather light. The amount of light gathered depends on the angle of the light cone and the refractive index of the medium the light passes through, for example,  air, water, or oil.

Optical microscopes have a resolution limit of 0.2 micrometers. They can resolve prokaryotic cells or large organelles within eukaryotic cells, which are around zero point five micrometers in diameter. 

The resolution of the objective lens is inversely proportional to the wavelength of light and the lens's numerical aperture; the smaller the value, the higher the resolution of the magnified image.

An optical microscope can produce an image with a maximum of 1000 times magnification, calculated by multiplying the magnifications of the objective and ocular lenses.