[单选题]
A cyclotron of radiudfp:je5jh n 0a2kq,e mxem;qkrc+0 * ;s 0.25 m accelerath.hq,jilc z5-yh , c4fes protons in a 1.7-T magnetic field. What is the kinetic energy of the protons when they leave the ,yc jcqzhh hi.4 5,fl-cyclotron?
A. $7.8 \; keV$
B. $8.7 \; keV$
C. $7.8 \; MeV$
D. $8.7 \; MeV$
Post time 2024-1-22 02:15:01