Numerical Aperture
The numerical aperture characterizes the light-gathering ability and resolution of an optical system, particularly microscope objectives.
Variables
Derivation
Related to the cone of light that can enter or exit the optical system. Higher NA means better resolution and light-gathering capability.
Your notes
Check value
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- n = 1.5 (Refractive index of medium)
- θ = 3 ° (Half-angle of maximum cone of light)
Result: NA = 0.07850393
Where this formula is listed
- Optics formulas, under Optical Instruments, alongside Magnifying Glass Magnification, Telescope Magnification, F-Number (f-stop) and Depth of Field.
- In the optics list it comes after Telescope Magnification and before F-Number (f-stop).
- Optics formula sheet, one of 34 formulas printed with symbol keys and SI units.
- The full formula index, grouped by category and topic.
Common questions
What is the Numerical Aperture formula?
Numerical Aperture is written NA = n sin θ. 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 sin θ?
In SI units, NA is numerical aperture (dimensionless); n is refractive index of medium (dimensionless); θ 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 sin θ.