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Please look at the diagram (a), and the textbook just mention that the incoming wave A will be interference constructively with wave B, but what about the reflective wave in the middle? why the wave in the middle not cancelling out the incoming wave since there is a 180 degree phase change? I really confused about this.
And another similar confusion is as below:
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In a dielectric wave guide, the wavefronts (or E-field) will interference constructively for incidence light at A and the reflective light at C, but what about the E-field creating from B to C, should that interferes with A and C either?
Please help! Thanks for your answers!