Purpose of ultraviolet microscope. ... The short wavelength of UV light helps to improve the image resolution beyond the diffraction limit of optical microscopesusing normal white light. The response of the sample to UV light is greater than that achieved by use of white light, in respect to the surroundings.

The principle behind fluorescence microscopy is simple. As light leaves the arc lamp it is directed through an exciter filter, which selects the excitation wavelength. ... The reflected light passes through the objective where it is focused onto the fluorescent specimen.

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https://www.jove.com/science-education/5040/introduction-to-fluorescence-microscopy