Optics

Numerical Aperture

NA=nsinθNA = n \sin\theta

The numerical aperture characterizes the light-gathering ability and resolution of an optical system, particularly microscope objectives.

Variables

NA
Numerical aperture
unitless
n
Refractive index of medium
unitless
\theta
Half-angle of maximum cone of light
°

Derivation

Related to the cone of light that can enter or exit the optical system. Higher NA means better resolution and light-gathering capability.

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Common questions

What is the Numerical Aperture formula?

Numerical Aperture is written NA = n sinθ. The numerical aperture characterizes the light-gathering ability and resolution of an optical system, particularly microscope objectives. It belongs to Optics, under Optical Instruments.

What are the units in NA = n sinθ?

In SI units, NA is numerical aperture (dimensionless); n is refractive index of medium (dimensionless); \theta is half-angle of maximum cone of light, measured in °.

How is the Numerical Aperture formula derived?

Related to the cone of light that can enter or exit the optical system. Higher NA means better resolution and light-gathering capability. The result is NA = n sinθ.