A light beam of wavelength 500 nm is incident on a metal having work function of 1.25 eV, placed in a magnetic field of intensity B. The electrons emitted perpendicular to the magnetic field B, with maximum kinetic energy are bent into circular are of radius 30 cm. The value of B is ___________ $\times$ 10^$-$7 T.

Given hc = 20 $\times$ 10^$-$26 J-m, mass of electron = 9 $\times$ 10^$-$31 kg