# ref_index1.0

Refractive index of air, and vacuum-air wave length conversion

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DEVELOPED BY:
Prasanth Nair
HOMEPAGE:
github.com
CATEGORY:
ROOT \ Science and Engineering \ Astronomy
ref_index is a Python tool for calculating refractive index of air, under varying atmospheric conditions. Functions for conversion of wave length of light in vacuum to that in air, and vice-versa are also defined.

The code is based on the documentation for the NIST online refractive index of air calculator.

Examples

Refractive index can be calculated using two different equations: one due to Edlén and another due to Ciddor.

>>> ref_index.ciddor(wave=633.0, t=20, p=101325, rh=20)
1.0002716285340578
>>> ref_index.edlen(wave=633.0, t=20, p=101325, rh=20)
1.0002716291691649
>>> ref_index.edlen(wave=633.0, t=20, p=101325, rh=80)
1.0002711197635226
>>> ref_index.ciddor(wave=633.0, t=20, p=101325, rh=80)
1.0002711183472626
>>> ref_index.edlen(wave=633.0, t=60, p=101325, rh=80)
1.0002339748542823
>>> ref_index.ciddor(wave=633.0, t=60, p=101325, rh=80)
1.0002340241754055

Conversion of wave length of light in vacuum to that in air, and vice-versa. Both of these functions use the Ciddor equation, as implemented in ciddor_ri() and ciddor().

>>> ref_index.vac2air(633.0)
632.82500476826874
>>> ref_index.air2vac(632.82500476826874)
633.00000139949032

>>> ref_index.vac2air(np.array([633.0, 550.0, 400.0]))
array([ 632.82500477, 549.84723175, 399.88692724])
>>> x = ref_index.vac2air(np.array([633.0, 550.0, 400.0]))
>>> ref_index.air2vac(x)
array([ 633.0000014 , 550.00000164, 400.00000243])

Note that the reversibility of air2vac() is ~1e-5nm.

Default temperature is 15∘C, pressure is 101325Pa, relative humidity is 0, and CO2 concentration is 450µmole/mole. All these can be changed.

>>> ref_index.vac2air(633.0, t=20, p=100000.0, rh=50)
632.83051710791892
>>> ref_index.air2vac(632.83051710791892, t=20, p=100000.0, rh=50)
633.00000131884678

For more details please see the docstring for the module. Detailed description of the equations can be found in the NIST documentation.

Installation

The module can be installed using pip and easy_install.

pip install ref_index

or,

easy_install ref_index

Last updated on October 12th, 2011

requirements