Since the colour phenomenon relies on the adjacency of light and dark , there are two ways to produce a spectrum : with a light beam in a dark room , and with a dark beam ( i.e. , a shadow ) in a light room .
Since the colour phenomenon relies on the adjacency of light and dark , there are two ways to produce a spectrum : with a light beam in a dark room , and with a dark beam ( i.e. a shadow ) in a light room .