1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Angle of Incidence and Reflection.

  1. Jun 23, 2009 #1
    Hi,

    Can someone please eloborate me why the Angle of Reflection is always same as the Angle of Incidence. I want the explanation at photon and molecular interaction level.

    Thanks in advance.

    - Pavan.
     
  2. jcsd
  3. Jun 23, 2009 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi Pavan ! Welcome to PF! :smile:

    I think it's simply conservation of energy and momentum …

    if no energy is lost (ie if the wavelength of each photon stays the same), and if the reaction force is normal to the surface (which it must be if the surface doesn't change shape), then the angles must be the same. :wink:
     
  4. Jun 23, 2009 #3
    Hi tiny-tim, Thanks for the Reply!!

    Actually I am only 50% satisfied still.

    What is it that the photon is interacting with?

    Lets say, I shine some light on a pool of water, what is it that is causing the "normal reaction"?

    Is the photon bouncing off the nucleus of Hydrogen and Oxygen atoms? If so, how?

    - Pavan.
     
  5. Jun 23, 2009 #4
    The actual mechanism of the interaction between the photon and the atoms in the material is a very complicated process as far as I know, but I can try to give you my amateur explanation.

    When the EM wave reaches the reflecting surface it slightly enters the material and interacts with the atoms. The atoms are bound together and electrically charged, which means that they are effectively working as balls connected by springs. The light wave makes the balls move, but they are retained by their bindings and therefore they start to oscillate. Oscillating charges means electromagnetic fields, which naturally has to be the opposite of their cause. A new EM wave is generated and sent in all directions but those who go back into the material will eventually be absorbed.

    This process depends on the structure of the atoms which is the reason why some materials almost let light pass right through it, some reflect most of it, and most do both.
     
  6. Jun 23, 2009 #5
    Hi Jame, Thanks for your reply.

    Can any one explain how prapogation of light through transparent objects work?

    How can most of the photons travel so perfectly aligned through a solid object?

    My another question is regarding Polarization. How do polarizors work?

    - Pavan.
     
  7. Jun 23, 2009 #6

    Andy Resnick

    User Avatar
    Science Advisor
    Education Advisor
    2016 Award

    It isn't, in general- only for specular reflection.
     
  8. Jun 23, 2009 #7
    Hi Andy,

    Could you please kindly answer the other questions in my earlier posts!!

    Thanks in advance.

    - Pavan.
     
  9. Jun 23, 2009 #8

    Andy Resnick

    User Avatar
    Science Advisor
    Education Advisor
    2016 Award

    I would be happy to help you understand any points you are not sure about- but I can't help you unless I have a better idea of what you understand already.
     
  10. Jun 24, 2009 #9
    Hi Andy,

    Thanks for your commitment to help others!!

    I have a decently good idea about physics. However, my understanding is limited to the "Principles" of it, and not the exact reason behind those principles.

    To start with, could you please tell me what an Electro-Magnetic wave exactly is? and how it is generated from an atom? And how does that wave prapogate in vacuum?

    Thanks in advance.
     
  11. Jun 24, 2009 #10

    Andy Resnick

    User Avatar
    Science Advisor
    Education Advisor
    2016 Award

    I'm not sure what electromagentic waves *are*, in all honesty. I know there are several ways of describing electromagnetic phenomena including a continuous field theory (waves), a quantized field theory (photons), or as rays (geometical optics).

    Propogating EM waves can be generated in a number of ways- including bound state transitions of an atom. In the wave picture, the wave propogates by itself:there need be no 'medium' in which the wave propogates.

    Does this help?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook