Thomson parabolas

Thomson parabolas

[′täm·sən pə′rab·ə·ləz]
(electromagnetism)
A pattern of parabolas which appear on a photographic plate exposed to a beam of ions of an element which has passed through electric and magnetic fields applied in the same direction normal to the path of the ions; each parabola corresponds to a different charge-to-mass ratio, and thus to a different isotope.