In a Young's double slit experiment, an angular width of the fringe is 0.35° on a screen placed at 2 m away for particular wavelength of 450 nm. The…

In a Young's double slit experiment, an angular width of the fringe is $\displaystyle 0.35$° on a screen placed at $\displaystyle 2$ m away for particular wavelength of $\displaystyle 450$ nm. The angular width of the fringe, when whole system is immersed in a medium of refractive index $\displaystyle 7 / 5$, is $\displaystyle \frac{1}{\alpha}$. The value of $\displaystyle \alpha$ is \_\_\_\_.