Given-
Kinetic energy of proton = K

Distance between the target and the accelerator = l

Therefore, radius of the circular orbit ≤ l

From question it is given that, the beam is bent by a

perpendicular magnetic field, let it be B.

We know-

Now, radius r -

where,

m is the mass of a proton

v= velocity of the particle

B = magnetic force

e= charge on the particle

For a proton, the above equation can be written as-

where r = l

Kinetic energy, K

Substituting the values of v in the equation (1)