I am a trainee science (specialising in physics) teacher. I upset my mentor a little bit by saying to a year 10 science class that there is "light" that people cannot see... by which I was referring to wavelengths of EM radiation that lie outside of the 400-700nm range. After the lesson, my mentor told me that I was wrong to use the term "light" when referring to wavelengths that we cannot see. He said that the word "light" refers only to wavelengths that we can see. He asked me to stop referring to invisible radiation as light. I was disappointed with this because: 1) I felt my use of the word light was correct. 2) I thought that it helped to communicate the idea that these other wavelengths of the EM spectrum are not in any fundamental way different from the wavelengths that are visibile to us - ie. I felt it helped to take the mystery or confusion away from what the EM spectrum is all about. Anyone care to offer their feedback?