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Δl
π
λ/2
π/2
λ/4
π/4
λ/8
π/8
λ/16
ΔP[dB]
−3.922
−0.912
−0.224
−0.056
r≥
d2/4λ
d2/2λ
d2/λ
2d2/λ
Usage
Photo depth of field
Antenna measurements
Lord Rayleigh 1891