A slit of width a is illuminated by light of wavelength λ. The linear separation between 1^st and 3^rd minima in the diffraction pattern produced on…

A slit of width $\displaystyle a$ is illuminated by light of wavelength $\displaystyle \lambda$. The linear separation between $\displaystyle 1^{\text {st }}$ and $\displaystyle 3^{\text {rd }}$ minima in the diffraction pattern produced on a screen placed at a distance $\displaystyle D$ from the slit system is $\displaystyle \_\_\_\_$.