Potential difference V = 5.5 x 104 V and given that the de Broglie wavelength l = h/m.v
h = 6.63 x 10-34 Js, me = 9.11 x 10-31 kg and charge qe = 1.6 x 10-19 C.
Then using ½.m.v2 = q.V yields velocity v = 1.4 x 108 m s-1.
Hence wavelength l = 5.2 x 10-12 m s-1 by substitution.
The correct chronological sequence is :- Roentgen, Ruska, Rohrer, Donald, Hounsfield and Damadian.
Common radioisotopes are :-
Technetium-99 as a gamma emitter produced in a reactor.
Thallium-201 as an X-ray and gamma emitter produced in a cyclotron.
Fluorine-18 as a gamma emitter produced in a cyclotron.
About 1.8 mSv subjected to g - radiation which is roughly the same as normal background yearly dose.