The Isaac Newton’s fits of easy transmission and easy reflection: models and contradictions

modelos e contradições

Abstract

Newton developed the concept of fits of easy transmission and easy reflection in order to explain the periodicity of colored rings in thin films. The fits are dispositions of the light rays to be reflected or refracted by the surface. Newton was not sure about the fits’ properties and their origin. Despite the fact Newton stated he would not consider the origin of the fits in order to avoid non-empirical hypothesis in his science, he took into account many different explanations for the fits. The present paper discusses the various models developed by Newton to explain the colours in thin plates, emphasizing their limits, contradictions and their hypothetical character.