I have two monochromatic beams, one green, one red. I combine the beams together and get a single yellow beam. I pass the yellow beam through a spectroscope and determine its spectrum. What do I see? A red band and a green band? A yellow band? I suspect that what I'd see is: A green band, a red band, a yellow band, a very low frequency band that is a carrier for the yellow, and other weaker bands that represent higher harmonics of the red+green combination. Can anyone confirm this? By the way, the low frequency carrier that I am suspecting will appear comes from the sum-to-product trig identity. http://en.wikipedia.org/wiki/List_of_trigonometric_identities The sum of the green and red cause a product of a yellow and a low frequency envelope.