need help on physics problem

Question

Light with a wavelength of 593 nm (5.93 x 10^-7 m) is incident upon a double slit with a separation of 0.6 mm (6 x 10^-4 m). A screen is located 7.5 m from the double slit.

(a) At what distance from the center of the screen will the second dark fringe appear?

Answer 1

Use the formula y=(m+1/2)λD/d to find the position of the minima. In this problem m=2 λ= 5.93x10^-7m d=.6mm and D= 7.5m. Using these values gives y= 3•5.93x10^-7•7.5/2•6x10^-4 m. Hence y= 11.11x10^-3 m. Therefore y= 11.11mm is the distance from center that the second dark fringe appears.