Monochromatic light passing through a single slit produces a diffraction pattern that consists of a bright central region surrounded by alternating light and dark bands (minima and maxima) as a result of constructive and destructive interference

Dark bands

The minima occur at angles $\theta _n$ that satisfy $sin \theta _n = \frac{n \lambda}{w}$ for $n = 1, 2...$

Light bands

The maxima occur at angles $\theta _m$ that satisfy $sin \theta _m = \frac{(m+\frac{1}{2}) \lambda}{w}$ for $m$ = 1, 2

• To find the maximum, omit the $m + \frac{1}{2}$ from the equation
• To find the angular width, multiply $\theta$ by 2

Distance between bands

Distance between successive minima and successive maxima is given by $y_1 = \frac{\lambda L}{w}$, and the width of the central maximum is $y_2 = 2 \triangle y_1$