[UPSC CSE 1991] Nuclear Physics (Q208, 60M)

Give, in short the principle of working of mass spectrograph (any type). What does it determine? What are isotopes? How many isotopes of hydrogen do you know of? Are they all stable? The minimum energy required for the disintegration of the nucleus of a stable isotope of hydrogen is 2.21\text{ MeV}. Calculate the mass of this nucleus in a.m.u.