The fact that the heat energy, which is added to the atoms, is released as light energy is proof of which Conservation Law?

Answer : It is the proof of Law of conservation of energy.

Explanation:

Law of conservation of energy : It states that the energy can not be created or destroyed. But it changed one state to another state or transferred from one object to another object.

For example : In case of bulb, energy in the form of electricity is converted into the light and heat. Hence energy is conserved.