A velocity selector uses a fixed electric field of magnitude E and the magnetic field is
varied to select particles of various energies. If a magnetic field of magnitude B is used to
select a particle of a certain energy and mass, what magnitude of magnetic field is needed
to select a particle of equal mass but twice the energy?
A. 0.50 B B. 1.4 B C. 2.0 B D. 0.71 B E. 1.7 B


請問有人會解嘛??

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