Reflectance
![Spectral reflectance curves for aluminium (Al), silver (Ag), and gold (Au) metal mirrors at normal incidence.](/Images/godic/202502/12/Image-Metal-reflectance4407.png")
![Fresnel reflection coefficients for a boundary surface between air and a variable material in dependence of the complex refractive index and the angle of incidence.](/Images/godic/202502/12/Fresnel_equations_-_reflectance.svg4407.png")
![Reflectance of smooth water at 20°C (refractive index 1.333).](/Images/godic/202502/12/Water_reflectivity4407.jpg")
Reflectance of the surface of a material is its effectiveness in reflecting radiant energy. It is the fraction of incident electromagnetic power that is reflected at an interface. The reflectance spectrum or spectral reflectance curve is the plot of the reflectance as a function of wavelength.