Part 1-Modern Physics
       The title of this section is not completely 
        accurate
       The theories and discoveries described originated 
        between 1895 and 1930
       In this time period, two major theories were advanced
           • Quantum physics
           • Einstein’s Theory of Relativity
       Both theories revolutionized the sciences and 
        technology
       Both theories present various aspects of nature in ways 
        that defy the familiar “commonsense” view of the 
        world.
        Wave-Particle Duality of Light
       Earlier, we learned that light can be represented as a wave 
         propagated by an interchange of energy between 
         periodically varying electric and magnetic fields.
       Electromagnetic radiation exhibits waves phenomena
        Diffraction
        Interference
        Doppler Effect
        Reflection
        Refraction
        Wave-Particle Duality of Light
       The wave model does not explain everything about light
       In other interactions, electromagnetic radiation (including 
         light) acts as if it is composed of particles possessing 
         kinetic energy and momentum
       Early in the 20th century, it was discovered that light 
         having a frequency above some minimum value incident 
         on certain metals caused electrons to be emitted from the 
         metal.
           • This phenomenon is known as “the photoelectric 
            effect”, and can’t be explained by the wave model 
            of light.
         The Photoelectric Effect
       What's the photoelectric 
         effect?
       It's been determined 
         experimentally that when 
         light shines on a metal 
         surface, the surface emits 
         electrons. For example, you 
         can start a current in a circuit 
         just by shining a light on a 
         metal plate. 
      Continuing
      More on the Photoelectric effect
      Caused when high frequency 
       electromagnetic waves strike 
       the surface of a metal
      Electrons at the surface of the 
       metal absorb the high 
       frequency light, then become 
       excited
      These excited electrons then 
       “jump off” the surface of the 
       metal, releasing their energy 
       as they do