Radiant heat travels in the form of waves. No physical contact between objects is needed to transfer heat by radiation. Students will fill black, white, and silver cans with water, and observe the temperature change in the water when the cans are placed under a bright lamp. The cans are being heated by radiation, and the color of the outer finish of the cans determines the efficiency with which they absorb the heat energy. The white and silver cans reflect most of the rays that strike them (visible and non-visible), so they will heat much more slowly than the black can.