6 × 10–19 C × 6 × 10–4 T)
                      = 28 × 10–2 m = 28 cm
n = v / (2 pr) = 17×106 s–1   = 17×106  Hz   =17 MHz E = (½ )mv 2   = (½ ) 9 × 10–31 kg × 9 × 1014 m2/s2  = 40 5 ×10–17 J
  ≈  4×10–16 J = 2 5 keV