n_air: Dispersion formula for the refractive index of air

In AlexCast/apsfs: Monte Carlo code for simulation of atmospheric Point Spread Functions and spatially-resolved Spherical Albedo Functions

Dispersion formula for the refractive index of air

Description

This function calculates the real part of the refractive index of standard dry air relative to vaccum. See details.

Usage

n_air(lambda)

Arguments

lambda

Wavelength in vacuum (nm).

Details

The dispersion model implemented is that by Ciddor (1996), for the refractive index of standard dry air. It is reference for dry air (0 moisture), 15 ºC, 101.325 Pa and 450 ppm CO2. This equation is recomended by Zhang et al. (2009) for the convertion of (saline) water refractive index relative to air to that relative to vacuum.

Ciddor (1996) also provides equations to account for different levels of CO2 and water vapor. Those are not implemented in the current version.

The valid range is 200 nm to 1100 nm. If the refractive index is requested outside this range, the function will return a warning.

Value

A numeric vector with the real part of refractive index of standard dry air (unitless).

References

Ciddor, P. E. 1996. Refractive index of air: new equations for the visible and near infrared. Applied Optics 35, 9, 1566-73. DOI: 10.1364/AO.35.001566

Zhang, X.; Hu, L.; He, M.-X. 2009. Scattering by pure seawater: effect of salinity. Optics Express 17, 7, 5698-710. DOI: 10.1364/OE.17.005698

Examples

# Get the refractive index for teh visible range: 
n_air(400:700) 

AlexCast/apsfs documentation built on Feb. 1, 2024, 9:48 p.m.