Light waves from two coherent surface arrive at two points on a screen with path differences zero and2/2. Find the ratio of intensities at the points.
Question
Light waves from two coherent surface arrive at two points on a screen with path differences zero and2/2. Find the ratio of intensities at the points.
Solution
The path difference between the two waves is λ/2, which corresponds to a phase difference of π (since 2π phase difference corresponds to λ path difference).
The intensity of a wave is proportional to the square of its amplitude. When two waves interfere, the resulting amplitude is the sum of the individual amplitudes.
In this case, because the phase difference is π (which corresponds to destructive interference), the resulting amplitude at the point with the path difference of λ/2 is zero (since the two waves perfectly cancel each other out).
Therefore, the intensity at this point is also zero.
The intensity at the point with zero path difference is simply the intensity of one of the waves (since they constructively interfere at this point).
Therefore, the ratio of the intensities at the two points is ∞:0, or simply ∞.
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