Quantitative shadowgraphy made easy

Abstract

This paper is dedicated to the learning of the shadowgraphy technique at graduate and undergraduate levels. It presents an experiment that allows measurement of the refractive index of butane with the help of an affordable quantitative shadowgraphy bench. The paper is constituted of two distinctive parts. The first presents the theory and data processing involved in shadowgraphy, introducing the concept of Abel inversion and modern data computer processing for graduate students. The second focuses on the experimental set-up and results; here, a qualitative interpretation of shadowgrams suitable for undergraduate students is given, as well as a quantitative explanation using a butane gas jet. The refractive index of butane measured with our simple experimental set-up is in close agreement with values available in the literature.