Calculating Slit Width from Monochromatic Light Diffraction | 616nm Wavelength

[inflames829]

Homework Statement

monochromatic light of wavelength 616nm is incident on a narrow slit. On a screen 1.7m away, the distance between the second diffraction minimum and the central maximum is 1.8cm. What is the width of the slit in mm?

Homework Equations

The Attempt at a Solution

For the question i use the formula lambda = y x w / L
where L is the length to screen, y is the distance between the middle of the bright spot and the first dark line and w is the slit width. I rearrange the equation to get w and then just pug in the values and I get w = lambda x L / Y and the answer i get is w = 616E-9 x 1.7 / 0.018 = 5.82E-5m, bbut this answer is incorrect, can someone please help me with whatim doing wrong

 

[Kurdt]

The question gives the distance to the second minimum not the first.