Wave Optics

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