Optionally, a light source can be provided with different coulour filters. The light source provides a photon of energy. With a red filter the ball jumps one step; with the blue filter the electron jumps two or three steps up the ladder. Radiation with the wrong light, say green light, leaves the ball in its ground state (on the floor), because that energy would leave the ball between energy levels. Invite students to make predictions about the results of different colours of light/different amounts of absorbed energy.