# A-level Physics (Advancing Physics)/Diffraction/Worked Solutions

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1. What is the width of the central bright fringe on a screen placed 5m from a single slit, where the slit is 0.01m wide and the wavelength is 500nm?

${\displaystyle {\frac {W}{L}}\approx {\frac {\lambda }{d}}}$

${\displaystyle {\frac {W}{5}}\approx {\frac {500\times 10^{-9}}{0.01}}}$

W = 250μm, but since this is only half the beam, the beam is 500μm wide.