Question:
A Young's double slit apparatus has slits separated by $0.28 \mathrm{~mm}$ and a screen $48 \mathrm{~cm}$ away from the slits. The whole apparatus is immersed in water and the slits are illuminated by the red light $(\lambda=700 \mathrm{~nm}$ in vaccum). Find the fringe-width of the pattern formed on the screen.
Solution:
