In a YDSE, the field amplitudes from the two slits are A and 2A. If I₀ is the maximum intensity, find the intensity at a point where the phase difference is φ.
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Question

In a YDSE, the field amplitudes from the two slits are A and 2A. If I₀ is the maximum intensity, find the intensity at a point where the phase difference is φ.

G1 Physics · Accepted Answer

With slit amplitudes A and 2A, resultant intensity is proportional to A²+4A²+4A²cosφ=A²(5+4cosφ). Since I₀=(A+2A)²=9A², I=(I₀/9)(5+4cosφ). Option C.