Measuring the Molecular Polarizability of Air

TL;DR

This paper updates the measurement of air's molecular polarizability using a Michelson interferometer, providing a precise value that aligns with accepted standards, enhancing educational experiments in optics.

Contribution

It offers a refined measurement of air's molecular polarizability through an improved interferometric method, updating the fundamental data used in optics education.

Findings

Measured molecular polarizability: 2.133 ± 0.032 × 10^{-29} m^3

Calculated refractive index of air: 1.0002651(66)

Results agree with accepted values

Abstract

We present an update of the "refractive index of air" experiment commonly used in optics and undergraduate advanced labs. The refractive index of air is based on the average molecular polarizability, which we measured from the period of the phase shift in a Michelson interferometer as a function of pressure. Our value of the average molecular polarizability of air is \gamma_mol = 2.133 \pm 0.032 \times 10^{-29} m^3 (95% CI) and from this we find the refractive index of air at atmospheric pressure to be n = 1.0002651(66), which is in agreement with the accepted value of n=1.000271375(6).