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# Concept of numerical aperture

In the interactive animation the concept of the numerical aperture is illustrated.

A collective lens is shown, which focuses a light beam. Depending on the numerical aperture, the light is focused at different positions.

The animation was developed as a offline application for Windows and Macintosh systems and for integration into Microsoft PowerPoint slides. The online version presented here serves as a preview. The exe or app file can be downloaded free of charge in the member area.

## Description

You see a lens that focuses several parallel beams. The shape of the lens and thus the numerical aperture can be changed via a virtual controller. The light beams are updated automatically.

The numerical aperture is an important measure for judging the resolution of an objective or a lens. In the case of a smaller numerical aperture, the angle at which the light beams are focused is acute. In principle, lenses with small opening angles have a lower resolving power than lenses with large opening angles.

The numerical aperture is calculated according to the following formula:

$$NA = n \cdot \sin{\sigma}$$

$NA$: Numerical Aperture
$n$: Refractive index of the medium
$\sigma$: Half opening angle

## General

Title: Concept of numerical aperture Teachers and lecturersSelf-learners Microsoft® Windows®Microsoft® PowerPoint®Apple® Macintosh® Enlargeable without lossNo installation required License Information About the security of the Flash Player

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