A thin infinite sheet charge and an infinite line charge of respective charge densities $+\sigma$ and $+\lambda$ are placed parallel at 5 m distance from each other. Points ' $P$ ' and ' $Q$ ' are at $\frac{3}{\pi} \mathrm{~m}$ and $\frac{4}{\pi} \mathrm{~m}$ perpendicular distance from line charge towards sheet charge, respectively. ' $\mathrm{E}_{\mathrm{P}}$ ' and ' $\mathrm{E}_{\mathrm{Q}}$ ' are the magnitudes of resultant electric field intensities at point ' $P$ ' and ' $Q$ ', respectively. If $\frac{E_p}{E_Q}=\frac{4}{a}$ for $2|\sigma|=|\lambda|$. Then the value of $a$ is $\_\_\_\_$ .