Skip to main content
This is a pre-production deployment of Warehouse. Changes made here affect the production instance of PyPI (
Help us improve Python packaging - Donate today!

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

Project Description

Code for calculating refractive index of air, under varying atmospheric conditions, is provided in this module. 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.


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)
>>> ref_index.edlen(wave=633.0, t=20, p=101325, rh=20)
>>> ref_index.edlen(wave=633.0, t=20, p=101325, rh=80)
>>> ref_index.ciddor(wave=633.0, t=20, p=101325, rh=80)
>>> ref_index.edlen(wave=633.0, t=60, p=101325, rh=80)
>>> ref_index.ciddor(wave=633.0, t=60, p=101325, rh=80)

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)
>>> ref_index.air2vac(632.82500476826874)

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

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


The module can be installed using pip and easy_install.

$ pip install ref_index


$ easy_install ref_index


All equations used in this module come from the documentation for the NIST online refractive index calculator, written by Jack A. Stone and Jay H. Zimmerman.

Please send comments and suggestions to the email id prasanthhn in the domain.

Release History

This version
History Node


Download Files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Filename, Size & Hash SHA256 Hash Help File Type Python Version Upload Date
(9.0 kB) Copy SHA256 Hash SHA256
Source None Oct 12, 2011

Supported By

Elastic Elastic Search Pingdom Pingdom Monitoring Dyn Dyn DNS Sentry Sentry Error Logging CloudAMQP CloudAMQP RabbitMQ Heroku Heroku PaaS Kabu Creative Kabu Creative UX & Design Fastly Fastly CDN DigiCert DigiCert EV Certificate Google Google Cloud Servers