a) e v B = m v^2/R
R = m v /(e B) = m vo sin @/(e B) =
= (9.1*10^(-31) * 2* 10^6 * sqrt(2)/2)/(2*1.602*10^(-19) m = 4*10^(-6) m
b) vo T sin @ = 2 pi R
vo T cos @ = L
dividendo tg @ = 1 = 2 pi R/L => L = 2 pi R = 6.283 * 4.02*10^(-6) = 2.5*10^(-5) m