Can you please provide some explanation for the following two questions? Or please provide some links. Thank you. 1.) How does a laser heat up a material? Does the material absorb a photon and the material's atom gets excited? - when the atom relaxes, it emit an energy equal to that of the photon? Even if this is so, doesn't it only mean that the material remains at the same temperature that it was before? - it absorbs the same amount of energy that it releases. 2.) Why is a laser visible only when it hits a surface?