# Physics

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Electrons are accelerated though a potential of 60V and then from a beam that hits two slits separated by 2.5x10^-8m. (a) What is the wavelength of these electrons (hint: first find the momentum)? (b) How far is the second order bright spot from the center spot on a screen 4.0m from the slits?

• Physics -

mv^2/2 = eU
v = sqrt(2•eU/m) = sqrt(2•1/6•10^-19•60/9.1•10^-31) = 4.6•10^6 m/s.
λ =h/p =h/m•v = 6.63•10^-34/9.1•10^-31•4.6•10^6 =1.6•10^-10 m.
d•sinφ = k•λ,
tanφ =x/L,
sinφ ≈tanφ,
x =k•λ•L/d = 2•1.6•10^-10•4/2.5•10^-8 =5.1•10^-2 m.

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