PHYSICSMR.BALDWIN MODERN PHYSICS5/14/14 AIM: How does light interact with matter? DO NOW: How does energy travel from one place to another? How is your food heated up in your microwave? What is the purpose of the ozone layer?

2 Light: Particles or Wave? The Wave-Particle Duality – Light behaves like a wave and have characteristics of a particle – The evidence for the description of light as waves was well established at the turn of the century when the photoelectric effect introduced firm evidence of a particle nature as well.photoelectric effect Light travels in packets of energy called photons

3 Energy Level Diagram Quantum Jump: As an electron jumps from a higher energy level to a lower energy level, by conservation of energy, a photon with an energy equivalent to the energy difference must be emitted.

Change in energy level is equal to the energy of the ejected photon A photon is emitted in the process of a quantum jump to a lower energy level. A photon is absorbed in the process of a quantum jump from a lower to higher energy level.

5 Line Spectrum of Hydrogen Gas