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Reflection of light - the physics of a mirror

  1. Mar 29, 2008 #1
    How does reflecting of a light works? In physics people keep talking about mirrors in lasers and optics, etc. but how does mirror works at sub-atomic level? Does the light wave simply excite the electron which then sends identical wave in opposite direction? Or does it simply bumps off a particle? Can mirror be heated by a laser?
  2. jcsd
  3. Mar 29, 2008 #2


    Staff: Mentor

    A mirror doesn't work at a sub-atomic level. Reflection is a type of wave behavior, and it only occurs when you have an interface that is smooth at the scale of a wavelength.
  4. Mar 29, 2008 #3
    So why does silver object reflect the light more clearly than a wood for example.
  5. Mar 29, 2008 #4


    Staff: Mentor

    There are two factors here.

    First, the smoothness of the surface at the level of a wavelength, a silver object is smoother than a wood object. It would be very difficult to smooth the wood to the same level without adding some sort of polishing agent, but if you made the silver rough like the wood it would not reflect as well as a smooth mirror. But it would still reflect better than the wood. (The same thing happens acoustically, a smooth rock wall makes a better echo than a jumble of rocks.)

    Second, the electrical properties. Silver is a much better conductor than wood. This means that E-fields can go much deeper in wood than in silver. In this sense (the ability to conduct and support E-fields) wood is much more like air than silver. Whenever two media are similar in terms of their wave properties you get less reflection and more absorption or transmission. (The same thing happens acoustically, a rock wall makes a better echo than a soft padded wall.)

    These are general features of wave behavior, and not specifically limited to light waves.
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