Intensity of a double-slit interference pattern is represented as: $I(\theta) \propto [\text{interference factor} \times \text{diffraction factor}]$. The diffraction factor is given by:
[where $\alpha = \frac{\pi a}{\lambda} \sin\theta, \beta = \frac{\pi d}{\lambda} \sin\theta$, $a$ is width of single slit and $d$ is slit separation]