In the division of amplitude interferometers discussed in the previous chapter, we selected N = 2 in Eq. (23.1) and ignored the higher order reflections from the optical components. These reflections are weak in intensity when low-reflectance surfaces are involved. This effect is illustrated in Fig. 24.1 for two parallel glass/air interfaces each having a reflectivity of 4%. The beams resulting from multiple reflections are orders of magnitude weaker than the beams resulting from the primary reflections. Thus, interference phenomena such as Newton rings are not affected by the higher order reflections.
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