The atmospheric extinction of light

TL;DR

This paper presents an educational experiment demonstrating atmospheric extinction caused by Rayleigh scattering using lasers and artificial atmospheres, with measurements showing spectral intensity decay at different depths.

Contribution

It introduces a practical setup for students to measure and analyze atmospheric extinction coefficients for different wavelengths using accessible equipment.

Findings

Measured extinction coefficients for red, green, and blue light in milky water.

Demonstrated wavelength-dependent Rayleigh scattering effects.

Compared measurements from a light meter and a photodiode system.

Abstract

An experiment is described that enables students to understand the properties of atmospheric extinction due to Rayleigh scattering. The experiment requires the use of red, green and blue lasers attached to a travelling microscope or similar device. The laser beams are passed through an artificial atmosphere, made from milky water, at varying depths, before impinging on either a light meter or a photodiode integral to a Picotech Dr. DAQ ADC. A plot of measured spectral intensity verses depth reveals the contribution Rayleigh scattering has to the extinction coefficient. For the experiment with the light meter, the extinction coefficients for red, green and blue light in the milky sample of water were 0.27, 0.36 and 0.47 cm^-1 respectively and 0.032, 0.037 and 0.092 cm^-1 for the Picotech Dr. DAQ ADC.