InterviewSolution
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InterviewSolution
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A slightly divergent beam of non-relatistic charged particles accelearated by a potential difference `V` propagates from a point `A` along the axis of a straight solenoid. The beacm is brought into focus at a distance `l` from the point `A` at two successive values of magnetic induction `B_(1)` and `B_(2)`. Find the spefic charge `q//m` of the particles. |
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Answer» The charged particles will traverse a helical trajectroy and will be focussed on the axis after traversing a number of turns. Thus `(l)/(v_(0)) = pi. (2pi m)/(q B_(1)) = (pi + 1) (2pi m)/(q B_(2))` So, `(n)/(B_(1)) = (pi + 1)/(B_(2)) = (1)/(B_(2) - B_(1))` Hence, `(l)/(v_(0)) = (2pi m)/(q(B_(2) - B_(1)))` or, `(l^(2))/(2qV//m) = ((2pi)^(2))/((B_(2) - B_(1))^(2)) xx (1)/((q//m)^(2))` or, `(q)/(m) = (8 pi^(2) V)/(l^(2) (B_(2) - B_(1))^(2))` |
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