light as a continuum We have an iron rod and it is connected to a power supply. One meter away there is a sheet of white paper hanging on a wall. Both the rod and the paper are unlit. Very slowly we increase the voltage passing through the iron rod. Very slowly the rod starts to glow a dull red and then as we increase the voltage the rod gets brighter and brighter. Simultaneously the sheet of white paper reflects the red glow of the rod and also gets brighter and brighter, The rod eventually glows a bright white and so the paper also reflects this light. The question is: At what moment did the light start to travel to the paper one meter away?