Answer:
0.545 m
Step-by-step explanation:
K. E = 26 MeV = 26 x 1.6 x 10^-13 J = 4.16 x 10^-12 J
B = 1.35 T
Let r be the radius of curvature
The formula for the kinetic energy of a cyclotron is given by

m = 1.67 x 10^-27 kg, q = 1.6 x 10^-19 c

r = 0.545 m