in this question, 2 rods (one iron and one copper) are placed so that one end of each is in the flame of a bunsen burner.after a while, the end of the iron bar glows red but the end of the copper rod does not glow. why?
iron molecules get heat energy and they jump to the high energy level obits, but it is not stable so they emit electromagnet energy and reduce their energy and go back to lower energy levels. this emitting energy packs are enough to be in range of infrared and red light energy. so they give red color. but cu also do this but emitting energy is not enough. so it is not.
Molten metal glows 'red hot' due to the emission of electromagnetic radiation within the visible spectrum.
