Visualizing Rayleigh Scattering through UV Photography

Abstract

tailored camera setup has been used to take photographs of the atmosphere and the environment as seen in the ultraviolet (UV) wavelength band. These photographs make visible what the human eye cannot normally perceive?in particular, the effects of the increasingly strong scattering of UV radiation by the molecular atmosphere. This scattering of sunlight by air molecules is commonly known as Rayleigh scattering, and its scattering efficiency is inversely proportional to the fourth power of the wavelength; the shorter the wavelength, the stronger the scattering. The blue color of the cloud-free sky is a well-known consequence of this, while it is also known that radiation in the UV band is even more diffuse than blue light. The UV photographs presented here demonstrate these effects of Rayleigh scattering. They show, for example, how clouds are much harder to distinguish from the background (the sky) in the UV than in the visible band, and how shadows tend to disappear in the UV. Thereby, these photographs provide intuitive insight into the physics of Rayleigh scattering, and help connect the typically abstract and theoretical information of textbooks and scientific articles with a more concrete understanding of the effects of Rayleigh scattering.