CHEMISTRY COMMUNITY

When is light emitted and when is it absorbed. Why was it positive on the midterm when light is absorbed? And What does it mean for light to be emitted or absorbed?

Light is emitted if there is a quantum drop, and light is absorbed when there is a quantum jump.

If there is a jump in energy levels then the light is absorbed. if there is a drop in energy levels then the light is emitted.

Light is absorbed when energy level increases (electron gets excited). Light is emitted when energy level decreases (electron goes back to ground state).

If light is absorbed, a system is receiving an input of energy, so the value is positive. If light is emitted, a system is releasing energy (essentially losing it), so the value is negative.