Bainbridge Mass Spectrograph
Category : JEE Main & Advanced
In Bainbridge mass spectrograph, field particles of same velocity are selected by using a velocity selector and then they are subjected to a uniform magnetic field perpendicular to the velocity of the particles. The particles corresponding to different isotopes follow different circular paths as shown in the figure.
(1) Velocity selector : The positive ions having a certain velocity v gets isolated from all other velocity particles. In this chamber the electric and magnetic fields are so balanced that the particle moves undeflected. For this the necessary condition is \[v=\frac{E}{B}\] and E, B and v should be mutually perpendicular to each other.
(2) Analysing chamber : In this chamber magnetic field B is applied perpendicular to the direction of motion of the particle. As a result the particles move along a circular path of radius
\[r=\frac{mE}{qBB'}\Rightarrow \frac{q}{m}=\frac{E}{BB'r}\] also \[\frac{{{r}_{1}}}{{{r}_{2}}}=\frac{{{m}_{1}}}{{{m}_{2}}}\]
In this way the particles of different masses gets deflected on circles of different radii and reach on different points on the photo plate.
Separation between two traces \[=d=2{{r}_{2}}-2{{r}_{1}}=\frac{2v({{m}_{2}}-{{m}_{1}})}{qB'}\].
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