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kjsingh1
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Homework Statement
A beam of electrons is accelerated from rest and then passes through a pair of identical thin slits that are 2 nm apart. You observe the first double-slit interference dark fringes occurring at ±20◦ from the original direction of the beam when viewed on a distant screen.
(A) Calculate the speed of the electrons.
(B) Through what potential difference were these electrons accelerated?
Homework Equations
sin(θ)=((m+1/2)λ)/a
(a=width)
f=c/λ
v=fλ
K=.5mv^2
V(Potential Difference) = K/e
The Attempt at a Solution
(A)
sin(θ)=((m+1/2)λ)/a
λ=asin(θ)/(m+1/2)
λ=(2*10^-9m)sin(20)/(1+1/2)
λ=4.56*10^-10
V=c=speed of light? since f=c/λ
(B)
K=.5mv^2=.5(9.1*10^-31)(3*10^8)^2
K=4.095*10^-14
V=K/e
V=(4.095*10^-14)/(1.602*10^-19)
V=255617.98 ?
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