A deuteron of kinetic energy 50keV is describing a circular orbit of radius 0.5m in a plane perpendicular to a magnetic field B. The kinetic energy of the proton that describes a circular orbit of radius 0.5m in the same plane with the same B is:
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In magnetic fields:
K=(q²B²r²)/(2m)
Lighter particles need more kinetic energy for the same orbit radius.
Step 1: Radius of circular motion in magnetic field:
r=(mv)/(qB)
Step 2: Kinetic energy:
K=(1)/(2)mv²=(q²B²r²)/(2m)
Step 3: For same r, B, and q:
K ∝ (1)/(m)
Step 4: Mass of deuteron is approximately twice that of proton:
Kp = 2Kd = 2×50 = 100keV