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Light Microscopy

Introduction

Light microscopy uses electromagnetic radiation in the ultraviolet or visible wavelength range to obtain a magnified image of an object. The resolution of the imaging is limited by the minimum focus of the radiation due to diffraction. For light microscopy the diffraction limit is approximately 1 um (10-6 m). Imaging objects smaller than 1 um is possible using electrons instead of light. High-resolution electron microscopy can image features as small as approximately 1 Å (10-10 m).


Microscopes

The simplest light microscope consists of an objective lens and an eyepiece. Microscope objectives and eyepieces usually consist complex lens systems of two or more lenses to correct for lens aberrations.

Schematic of a light microscope

The objective lens forms a real intermediate image which is then greatly magnified by the eyepiece. The objective lens and eyepiece are maintained at a fixed distance and focusing is achieved by moving the whole assembly up and down in relation to the sample. High magnification requires very bright illumination of the sample and a condensor lens is usually placed between the light source and the sample stage to focus light onto the sample.


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