If a body is irradiated with radiation of wavelength \(\lambda\), and a fraction \(a(\lambda)\) of that radiation is absorbed, the remainder being either reflected or transmitted, \(a(\lambda)\) is ca...If a body is irradiated with radiation of wavelength \(\lambda\), and a fraction \(a(\lambda)\) of that radiation is absorbed, the remainder being either reflected or transmitted, \(a(\lambda)\) is called the absorptance at wavelength \(\lambda\).