single-slit diffraction pattern is formed when light of 680.0 nm is passed through a narrow slit. The pattern is viewed on a screen placed one meter from the slit. What is the width of the slit (mm) if the width of the central maximum is 2.69 cm?

Answer 1

Use the single-slit diffraction formula for the angular distance between the two minima on either side of the maximum. If you need a refresher course on that, see

http://en.wikipedia.org/wiki/Diffraction

That angle is given (for small angles) by
theta = 2 (wavelength)/d

Set that angle (in radians) equal to 2.69/100 = 0.0269

Then solve for the slit width, d.