Final answer:
To change the path of an ion in a mass spectrometer, one can adjust the strength of the magnetic or electric field, which will alter the ion's curvature path depending on its mass-to-charge ratio.
Step-by-step explanation:
In a mass spectrometer, 14N+ and 15N+ ions follow different paths due to the different mass-to-charge ratios resulting from their differing atomic masses. To change the path of an ion in the mass spectrometer, one could alter the strength of the magnetic field through which the ions travel. Since the path curvature of a charged particle in a magnetic field is related to its mass, modifying the magnetic field strength will influence how much the path of an ion is deflected.
Additionally, changing the electric field within the velocity selector can also affect the ions' paths. By tuning the velocity selector, only ions with certain velocities are allowed through, changing which ions reach the detector. Mass spectrometers often couple these adjustments with sensitive detectors to analyze a sample's molecular composition accurately. If the velocity is held constant, the radius of the ion's path, 'r', can become a direct measure of the ion's mass when the magnetic field strength 'B' is varied.