What will be the magnitude of the electric field at point $O$ as shown in the figure? Each side of the figure is $l$ and perpendicular to the other?

• A

  $\frac{1}{4\pi {\epsilon }_0}\frac{q}{l^2}$
• Correct answer
  B

  $\frac{1}{4\pi {\epsilon }_0}\frac{q}{\left(2l^2\right)}(2\sqrt{2}-1)$
• C

  $\frac{q}{4\pi {\epsilon }_0(2l{)}^2}$
• D

  $\frac{1}{4\pi {\epsilon }_0}\frac{2q}{2l^2}\left(\sqrt{2}\right)$

Hence, the correct answer is option: 'B'.