A circular lamina of radius 'R' is having surface charge density $σ\, cm^{-2}$. Electric field at axial distance $'2R'$ is

$\frac{σ}{4\pi \epsilon_0 R^2}$

The correct answer is option (1) : $\frac{σ}{4\pi \epsilon_0 R^2}$

$E=\frac{σ}{2\epsilon_0}(1-cos \phi )$, where $cos \phi =\frac{2R}{\sqrt{4R^2+R^2}}$

$E=\frac{σ}{2\epsilon_0}\left(1-\frac{2}{\sqrt{5}}\right)$

NA