A uniformly charged disc of radius \( R \) having surface charge density \( \sigma \) is placed in the \( xy \) plane with its centre at the origin. Find the electric field intensity along the \( z \)-axis at a distance \( Z \) from origin:
$E = \frac{2\epsilon_0}{\sigma}\left(\frac{1}{(Z^2 + R^2)^{1/2}} + Z\right)$
$E = \frac{\sigma}{2\varepsilon_0}\left(1 + \frac{Z}{(Z^2 + R^2)^{1/2}}\right)$
\( E=\dfrac{\sigma}{2\varepsilon_{0}}\left(1-\dfrac{Z}{\left(Z^{2}+R^{2}\right)^{1/2}}\right) \)
\( E=\dfrac{\sigma}{2\varepsilon_{0}}\left(\dfrac{1}{Z^{2}+R^{2}}+\dfrac{1}{Z^{2}}\right) \)
