Question about brewster's angle

  1. except the maths. methods
    can anyone explain why the reflected light is polarised while the refracted light is partially polarised in brewster angle ,please??
  2. jcsd
  3. If the incident light is unpolarized, the light reflected at Brewster's angle will include only one polarization (100% polarized), and the refracted light will include all the light of the other polarization.
    Bob S
  4. clem

    clem 1,276
    Science Advisor

    The polarization is determined by the Fresnel coefficients for reflection and refraction. The Fresnel coefficient for polarization parallel to the plane of incidence vanishes, while the coefficient for refraction does not. This is most easily seen from the algebra.
  5. YUP That's brewster's law
    but what's the principle behind it ???

    What's the fresnel coefficients ???
  6. Fresnel's equations for the transverse E and H components of light match the incident, reflected and refracted tangential components of E and H at the boundary.
    Bob S
  7. clem

    clem 1,276
    Science Advisor

    That's your problem. Buy a textbook.
  8. jtbell

    Staff: Mentor

    They can be derived from Maxwell's equations by applying the boundary conditions for E and B fields to an electromagnetic wave at a reflecting/refracting surface.
  9. [OFF TOPIC] What maths's level is required the above equation???
    furthermore, at brewster's angle , what is the source of the reflected light ???
  10. kor-
    You have been given several good references. Now read them. When you have, I would like you to solve the following real-world situation. You are fly-fishing in a high-elevation trout lake on a beautiful clear-blue (hint) morning. You are facing south, roughly 90 degrees away from the sun, at your left shoulder. Why can you see the fish clearly? Why is the reflection of the sky in the water pitch black? Read
    Bob S
  11. although I still dont understand it (it needs time ), thank you for your help :smile:
  12. In Rayleigh scattering of sunlight in clear unpolluted air, the light scattered at 90 degrees is completely polarized such that the E vector is perpendicular to the plane of scattering. In the url I posted previously

    read the paragraph

    "Light from the Sun is unpolarized. However, when it is scattered it becomes polarized, because light is scattered preferentially in some directions rather than others. Consider a light-ray from the Sun which grazes the Earth's atmosphere. The light-ray contains light which is polarized such that the electric field is vertical to the ground, and light which is polarized such that the electric field is horizontal to the ground (and perpendicular to the path of the light-ray), in equal amounts. However, due to the factor in the dipole emission formula (1119) (where, in this case, is the angle between the direction of the wave electric field and the direction of scattering), very little light is scattered downward from the vertically polarized light compared to the horizontally polarized light. Moreover, the light scattered from the horizontally polarization is such that its electric field is preferentially perpendicular, rather than parallel, to the direction of propagation of the solar light-ray (i.e., the direction to the Sun). Consequently, the blue light from the sky is preferentially polarized in a direction perpendicular to the direction to the Sun. "
    On a clear blue-sky day, get a polarizing filter and look at the sky at 90 degrees to the sun (where a single photon scattering would be 90-degree scattering), and observe the polarization of blue light.
    Bob S
    Last edited: Nov 9, 2009
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