Light is basically a tiny electromagnetic wave that travels through space

Light is basically a tiny electromagnetic wave traveling through space.The top of a wave is called its crest and the distance between two crests
is called the wavelength.The crests in red light are about 700 billionths of a meter apart and the wavelength of purple light
is even shorter,about 400 billionths of a meter,or 400 nanometers.When light hits the thin front surface of a bird's hollow melanosome,
some is reflected and some passes through.