1. The problem statement, all variables and given/known data An experiment was performed in which neutrons were shot through two slits spaced 0.10 mm apart and detected 3.5 m behind the slits. The following figure shows the detector output. Notice the 100 μm scale on the figure. To two significant figures, what was the speed of the neutrons? 2. Relevant equations Δy = λL/d (spacing between maxima) λ = h/mv (de Broglie λ) m= 1.67*10^-27 Kg 3. The attempt at a solution The spacing between the maxima appears to be 100*10^-6 m in the figure, so: (Δy*d)/L = λ = ((100*10^-6 m)*(0.1*10^-3 m))/3.5 m = 2.85714*10^-9 m = de Broglie λ v = h/(mλ) = (6.626*10^-34 J.s)/((1.67*10^-27 Kg)*(2.85714*10^-9 m) = 138.9 m/s This answer is incorrect. Can someone please give me a hint as to what I'm doing wrong?