An infinite line charge produces an electric field of $9 × 10^6 N/C$ at a distance of 20 cm. The linear charge density will be:

$10^{-4} C/m$

The correct answer is Option (2) → $10^{-4} C/m$

To calculate the linear charge (λ) of an infinite line charge -

$E=\frac{λ}{2πε_0r}$

where,

$E=9×10^6N/C$

$r=20cm=0.2m$ (distance from line charge)

$∴λ=2π(8.85×10^{-12})(0.2)(9×10^6)$

$=10^{-4}C/m$