In terms of ground state and excited state how can we view light?

How do you identify the anode on a power source such as a battery? how do you identify the cathode? how are terms anion and cation?

Alidded glass container is filled with a colored gas. after a period of time, it is observed that the gas is uniformly spread throughout the box and that the movement has slowed considerably. next, a warm iron plate is carefully placed under the box. why is there resumed movement of the gas in the container?

What are the constituent metals of stainless steel?