Q. In Young’s double slit experiment the separation $d$ between the slits is $2\, mm$, the wavelength of $\lambda$ the light used is $5896 \mathring A$ and distance $D$ between the screen and slits is $100\, cm$. It is found that the angular width of the fringes is $0.20^{\circ}$. To increase the fringe angular width to $0.21^{\circ}$ (with same $\lambda$ and D) the separation between the slits needs to be changed to
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