What is the wavelength of the light?
Since the light moves like a periodic oscillation through space, one can measure the distance between two points of the same phase on this oscillation, thus for example between two “wave mountains” or maxima.
The greek letter lambda represents the wavelength and its SI unit is nanometer (nm). The wavelength of the light determines its color. The human eye can perceive from about 380 nm (violet) to 780 nm (red) light. About 780nm is the infrared and under 380 nm the ultraviolet range.