1. A wave based explanation for double slit diffraction patterns You will need: A compass, with the centre screw firmly tightened A sharp pencil A sheet of A4 graph paper A 30cm ruler.

2. A wave based explanation for double slit diffraction patterns Place your graph paper on the desk (landscape orientation). Make small pencil marks on the long edge along the bottom of the paper, at 12cm and 16cm. Set your compass to a radius of 1cm. Draw a semicircle, centred on the mark at 12cm. Draw a second semicircle, centred on the mark at 16cm. Repeat this process, with the compass radius set at 2cm, 3cm, 4cm, 5cm, 6cm and 7cm.

3. A wave based explanation for double slit diffraction patterns Draw a small dot, preferably in red ballpoint pen, in each place a wave crest meets another wave crest.

4. A wave based explanation for double slit diffraction patterns ….Like this….!

5. A wave based explanation for double slit diffraction patterns The dots should line up to show where we are getting constructive interference. Join the points with lines to show where the bright fringes will occur.