When \(0.5\,\text{\AA}\) X-rays strike a material, the photoelectrons from the K-shell are observed to move in a circular path of radius \(23\,\text{mm}\) in a magnetic field of \(2 \times 10^{-2}\,\text{T}\), perpendicular to the direction of emission of photoelectrons. What is the binding energy of K-shell electrons?
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Magnetic field gives momentum directly:
\[
p=eBr
\]
Then use photoelectric equation.