equation e above shows that cos is imaginary in the case of total internal refle
ID: 1769737 • Letter: E
Question
equation e above shows that cos is imaginary in the case of total internal reflection. The wave function for the electric vector of the transmitted wave is then expressible as where 2.67) in = k', and The factor e- in Equation (2.67) shows that the evanescent wave amplitude drops off very rapidly as we proceed away from the boun- dary into the rarer medium. The complex exponential factor eack- indicates that the evanescent wave can be described in terms of sur- faces of constant phase moving parallel to the boundary with speed alki. It is easy to show that this is greater by the factor 1 /sin than the phase velocity of ordinary plane waves in the denser medium. That the wave actually penetrates into the rarer medium can be demonstrated experimentally in several ways. One way is shown in Figure 2.15. Two 45-90-45-degree prisms are placed with their long Glass Glass Figure 2.15. A method for illustrating the penetration of light into the rare medium. faces close together but not in actual contact. Light from a source S is found to be partially transmitted, the amount depending on the sepa- ration of the prism faces. This arrangement can be used to make such things as variable output couplers for lasers. In another experiment, first demonstrated by Raman, reflection of light was found to occur from a sharp metallic edge placed near, but not in contact with, the lu raflecting prism as shown in Figure 2.16.Explanation / Answer
#The highlighted portion tries to explain the two triangular arranged in a single arrangement without touching each other.
-This experiment says that if two triangular prisms are placed in the square type arrangement without touching each other surfaces as you can see in the figure shown in the question , then light transmitted from one side of prism will pass through both the prisms . But the amount or ratio of light passing through each prism will depend on the distance of separation. (I.e how far they are placed from each other).
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