Monochromatic light falls on two narrow slits separated by $0.1\ \text{mm}$. A pattern of bright and dark fringes appears on a screen $2.0\ \text{m}$ away. The spacing between neighbouring bright fringes is $8.0\ \text{mm}$. What path difference exists between the light waves from the two slits at the second order dark fringe?
- A$2.0 \times 10^{-7}\ \text{m}$
- B$4.0 \times 10^{-7}\ \text{m}$
- C$6.0 \times 10^{-7}\ \text{m}$
- D$8.0 \times 10^{-7}\ \text{m}$