Answer:
b.4
Step-by-step explanation:
Let
Magnetic field produced=B
Charge on particle=q
Mass of charged particle=m
Radius=2r
We have to find the k.E of the particle by what factor increases when radius taken twice .
Maximum K.E of particle in cyclotron=

Substitute radius= 2r
Then, maximum kinetic energy of particle =

Hence, the maximum kinetic energy of the particle increases by 4 when radius taken twice.
Answer: b.4