Week 2
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    This week begins with a review of electromagnetic waves.   Following that will be the photoelectric effect, blackbody radiation, the Compton effect and other photon processes.  The week will end with a description of a photon.  

    We are learning about the dual nature of light which behaves both as a wave and a particle.  The wave nature of light is best viewed using a simple interference pattern.   Two coherent light sources will constructively and destructively interfere depending on the position in space.   View these two applets of two source interference and answer the question below.  

       1.  What is constructive interference?  What is destructive interference?

       2.  What does coherent mean in the context of waves?

       3.  So if both sources are coherent why do the destructive interference points have waves Pi/2 out of phase?

Photoelectric Effect

    The photoelectric effect is when electrons are emitted from a metal surface who has a sufficiently high enough energy of  electromagnetic waves incident upon it.   View this applet keeping in mind this will be one of the experiments we do this year.

       1.  What is required to remove an electron from the metal surface?

       2.  Higher energy electromagnetic radiation has longer or shorter wavelengths?

       3.  Will an energy increase past the work function of an electron increase the current read on the ammeter?   If not what will?

Blackbody Radiation

    Objects that have a temperature above absolute zero (all of them) undergo thermal radiation.   The intensity and energy of this electromagnetic thermal radiation increases as temperature increases.   View this applet to see this basic radiation observed for different temperatures. (the tab "new graph" does not work correctly)

       1. The Sun's surface temperature is about 6000º Kelvin.  Using this applet can you explain why the sun appears as "white light."  

       2.  What is the relation between the maximum wavelength and the temperature?  Energy and temperature?

       3.  How does the luminosity of a black body depend on temperature?  How about the radius? 

Compton Scattering

    Electromagnetic radiation can interact with atoms in many ways.   One such way is through Compton scattering.  This is when a photon scatter from loosely bound, nearly free electrons.  In this process the electron is given enough energy to by emitted from the atom.  The energy given to the electron in the form of kinetic energy.  The photon that is scattered thus has less energy.  View both these applets and answer the questions. 

       1.  At what angle is the least energy transferred to the electron?

       2.  At what angle is the most energy transferred to the electron?  What does conservation of momentum have to do with this?

Scattering applets

    Here is a few more applets with other forms of scattering to visualize.  There is no questions associated with these applets.