1. 13.4 Double slit interference

2. From one source and two gaps 1 st bright fringe 1 st bright fringe central fringe

3. From one source and two gaps 1 st bright fringe 1 st bright fringe central fringe - the closer the slits become the wider the fringe separation. - waves of short wavelength give narrow fringe separation because blue light diffracts less.

5. Path difference Phase difference

6. Path difference Phase difference

7. W First bright fringe Central fringe screen Double Slit interference - theory

8. W First bright fringe Central fringe screen Double Slit interference - theory Ə D = wavelength = 600nm D = slit to screen distance = 2m S = slit separation = 0.5 mm W = fringe width = 1mm

9. For constructive interference at the screen: ( ie a bright fringe ) Wave fronts from S1 and S2 must arrive at the screen in phase with a path difference of a whole number of wavelengths

10. For constructive interference at the screen: ( ie a bright fringe ) Wave fronts from S1 and S2 must arrive at the screen in phase with a path difference of a whole number of wavelengths For destructive interference at the screen: ( ie a dark fringe ) Wave fronts from S1 and S2 must arrive out of phase with a path difference of half a wavelength

11. soh cah toa