Aman Sharma posted an Question
January 10, 2022 • 12:24 pm 30 points
  • IIT JAM
  • Physics (PH)

To prove upon reflection at an optically denser medium the phase of em wave shifts by 180° if incident light is oblique to the surface?

To prove upon reflection at an optically denser medium the phase of EM wave shifts by 180° if incident light is oblique to the surface?

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  • Aman sharma

    This method is good but can't we use reflection coefficient method for oblique incidence as we did for normal incindence of light?

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    yes. reflection coefficient can be used for any angle of incidence

  • Isha lohan 1 best-answer

    This is a general property of waves. If you have waves reflecting off a clamped point (like waves running on a string that you pinch hard at one point), the waves get phase inverted. The reason is the principle of superposition and the condition that the amplitude at the clamped point is zero. The sum of the reflected and transmitted wave must be the amplitude of oscillation at all points, so that the reflected wave must be phase inverted to cancel the incoming wave. This property is continuous with the behavior of waves going from a less massive string to a more massive string. The reflection in this case has opposite phase, because the more massive string doesn't respond as quickly to the tension force, and the amplitude of oscillation at the contact point is less than the amplitude of the incoming wave. This means (by superposition) that the reflected wave must cancel part of the incoming wave, and it is phase reflected. Without the phase change energy (and momentum) conservation would not be satisfied. Mathematically, it can be proved, as below. Although the theoretical proof is much better explanation.

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