IB Physics C3 Notes

Remember that a single-slit diffraction pattern contains a central maximum intensity followed by minima and maxima of decreasing amplitude and intensity, as shown below:

To calculate the angle of the first minimum (θ), based on slit width (b) and wavelength (λ), use the formula:

$sin \theta = \frac{\lambda}{b}$

If the angle is less than 12.5°, small angle approximation can be used, changing the formula to:

$\theta = \frac{\lambda}{b}$

The relative intensities and amplitudes of the first few maxima are outlined in the table below: