Fringe width (distance between consecutive bright or dark fringes): $\beta = \frac{\lambda D}{d} \quad [\text{L}], \quad \text{SI unit: m}$

Bright fringe positions (from center): $y_n^\text{bright} = n\beta = \frac{n\lambda D}{d}, \quad n = 0, \pm1, \pm2, \ldots$

Dark fringe positions (from center): $y_n^\text{dark} = \left(n - \frac{1}{2}\right)\beta = \frac{(2n-1)\lambda D}{2d}, \quad n = 1, 2, 3, \ldots$

Effect of changing parameters:

Pattern with white light:

• Central fringe: white (all $\lambda$'s have $\Delta = 0$)
• Higher-order fringes: colored (violet innermost, red outermost)
• After a few orders: colors overlap → pattern unrecognizable