Electromagnetism - Gauss' Law

An infinite, uniformly charged sheet with surface charged density σ cuts through a spherical Gaussian surface of radius R at a distance x from its center, as shown in figure. The electric flux Φ through the Gaussian surface is:

A.  πR²σ / ε0
B.  2πR²σ / ε0
C.  π(Rxσ / ε0
D.  π(R² −  x²)σ / ε0
E.  2π(R² −  x²)σ / ε0
(GR0177 #60)
Solution:

The Gaussian surface marks a circle around the plane with radius:  
r² = R² −  x²
The net charge within the Gaussian surface:
qenc = σA = σπr² = σπ(R² −  x²)
Electric Flux:
Φ = qenc / ε0 = σπ(R² −  x²) / ε

Answer: D

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