But in white light........green comes before blue..................it starts at a lower intensity and moves up......Red being the least intense..............ending in violet.......the most intense.......but DC's metro is out of order............i wonder why......

his comes up everytime I teach physics for elementary education majors. The curriculum I use (Physics for Everyday Thinking – which is awesome) says that the colors in white light are ROYGBV (Red-Orange-Yellow-Green-Blue-Violet). Typically, I will get a student that says “Hey! What about indigo? Shouldn’t it be ROYGBIV?” My first reaction to this was “huh?” Really, does it matter? Here is the spectrum you would see looking at a white light source.

You could break this into as many or as few colors as you like. So, it doesn’t really matter. But this leads to a great question: Who did this, and why is it that way (I guess that is two questions). Let me add a third: why do all the textbooks have the ‘I’ for indigo (although they all don’t, but many of them do).