A2 6 Conditions for Air to Cast a Shadow

Abstract

Air is transparent and does not absorb or reflect much light, hence it is improbable to have a shadow. In this article, we determine the conditions under which air can have a visible shadow comparable to the shadow of glass. This is done with refraction, by changing air's refractive index to that of glass, n=1.5. At a temperature of 0^oC, the air pressure needed to cast this shadow was found to be 1.57x10^8 Pa, analogous to the pressure used in high-pressure hydraulic hoses [5]. These are thought to be reasonable conditions to see the shadow of air.