Hi,

I am studying single slit diffraction now. The textbook shows to calculate the constructive interference, I should use constructive interference, which is Xm = (m + ) L/w (m=0,1,2,3...).

But when I ask course hero for the following question

Light with a wavelength of 488 nm is incident on a single slit with a width of 6.23 x 10^-4 m. If the screen is 2.7 m away, what is the distance to the first antinodal line?

Couse Hero tutor is using the destructive interference equation Xm = m L/w (m=0,1,2,3...).

Why? is it first antinodal line a bright fringe which is a constructive interference?

Now I am confused. Could you explain which one is correct? why?

Thanks