InterviewSolution
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InterviewSolution
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In mass spectrometer used for measuring the masses of ions, the ions are initaily accerlerated by an electric potential `V` and then made to describe semicircular paths of radius `R` using a magnetic field `B`.if `V` and `B` are kept constant, the ratio `(("charg e on the ion")/("mass of the ion"))` will be propertional to:A. `1/R`B. `(1)/(R^(2))`C. `R^(2)`D. R |
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Answer» Correct Answer - B The radiue of the orbit in which ions moving is determinet by the relation as given below `(mv^(2))/(R)=qvB` where m is the mass, v is velocity, q is charge of ion and B is the flux density of the magnetic field, so that qvB is the magnetic force acting on the ion, and `(mv^(2))/(R)` is the centripetal force on the ion moving in a curved path of radius R. about the verical field B is given by `omega=(v)/(R)=(qB)/(m)=2piv` where v is frequency. Energy of ion is given by `E=(1)/(2)mv^(2)=(1)/(2)m(Romega)^(2)` `=(1)/(2)mR^(2)B^(2)(q^(2))/(m^(2))` or `E=(1)/(2)(R^(2)B^(2)q^(2))/(m)" "......(i)` Form Eqs. (i) and (ii), we get `qV=(1)/(2)(R^(2)B^(2)q^(2))/(m)` or `(q)/(m)=(2V)/(R^(2)B^(2))` If V and B are kept constant, then `(q)/(m)prop(1)/(R^(2))` |
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