English Dictionary

Fresnel number

noun

(optics) A dimensionless quantity (denoted F), such that for an electromagnetic wave passing through an aperture and hitting a screen, F=(a²)/(L𝜆) where a is the characteristic size (e.g. radius) of the aperture, L is the distance of the screen from the aperture, and 𝜆 is the incident wavelength.

The Fresnel number is a dimensionless quantity used in optics.

意味（1）

(optics) A dimensionless quantity (denoted F), such that for an electromagnetic wave passing through an aperture and hitting a screen, F=(a²)/(L𝜆) where a is the characteristic size (e.g. radius) of the aperture, L is the distance of the screen from the aperture, and 𝜆 is the incident wavelength.