Class 12 NEET Physics Atoms and Nuclei Part 1

In mass spectrometer when ions are accelerated through potential V

1

2

mv2=qV ...(i)
where m is the mass of ion, q is the charge of the ion.
As the magnetic field curves the path of the ions in a semicircular orbit
∴ Bqv=

mv2

R

⇒v=

BqR

m

......(ii)
Substituting (ii) in (i), we get

1

2

m[

BqR

m

]2=qV or,

q

m

=

2V

B2R2

since V,B are constants,

q

m

∝

1

R2

or,

charge on the ion

mass of the ion

∝

1

R2