What does the nm mean on WAVELENGTH 650nm?

The initials "nm" in "650nm" stand for nanometers, it refers to wavelength, and is 1 billionth of a meter long. In the case of 650nm we're talking about a visible section of the electromagnetic spectrum, and in particular it describes light that is red. A red light laser pointer that produces 650nm light costs about $15.

Updated on Wednesday, February 01 2012 at 04:31PM EST
Collection: metric system