ABSTRACT
We know from our observation of rainbows that visible light (white light) is composed of a continuum of colors from violet to red. If a beam of white light is passed through a beaker of water, it remains white. If potassium permanganate is added to the water, the white light appears purple after it passes through the solution. The permanganate solution allows the red and blue components of white light to pass through but absorbs the other colors from the original beam of light. This is one example of the interaction of electromagnetic radiation, or light, with matter. In this case, the electromagnetic radiation is visible light and we can see the effect of absorption of some of the light with our eyes. However, interactions between electromagnetic radiation and matter take place in many ways and over a wide range of radiant energies. Most of these interactions are not visible to the human eye but can be measured with suitable instruments.
