試題詳解

4. A mass spectrometer works by ionizing atoms or molecules, and then accelerating them through oppositely charged plates. The mass is obtained by
(A) measuring the force of impact on a detecting screen, and then calculating the mass using force = mass × acceleration.
(B) suspending the ions in an applied electric field, and then calculating mass by the setting the downward gravitational force equal to the upward electrostatic force.
(C)measuring the magnitude of deflection as the ions pass through a magnetic field to obtain the charge-to-volume ratio, and then calculating the mass from that ratio.
(D) measuring the time it takes for the ions to hit the detector at a known distance to calculate the acceleration, and then calculating mass from force = mass × acceleration.
(E) all are not correct.