Two isotoprs of uranium U235(3.9x10^-25 kg) , U238(3.95x10^-25kg) into spectrometer (1.05x10^5 m/s). Each isotope is singly ionized and B field(0.75T). What is the distance between the two isotopes?

1 Answer
Apr 2, 2016

0.875cm0.875cm

Explanation:

Given that two isotopes of Uranium "U"235(3.9xx10^-25 kg) and "U"238(3.95xx10^-25kg)U235(3.9×1025kg)andU238(3.95×1025kg) into spectrometer.
Velocity of each singly ionized atom is 1.05xx10^5 m//s1.05×105m/s
Force vecF Fon a charged particle due to magnetic field =q(vecvxxvecB)=q(v×B)

Since the magnetic field is perpendicular to the direction of motion in a spectrometer
|vecF|=q.|vecv|.|vecB|F=q.v.B, singly ionized atom has charge 1.60xx 10^-19C1.60×1019C

This magnetic force produces circular motion of the ion.
Centripetal force (m.v^2)/r=|vecF|m.v2r=F, where rr is the radius of circle in which ion moves.
(m.v^2)/r=q.|vecv|.|vecB|m.v2r=q.v.B, Solving for rr
r=(m.|vecv|)/(q.|vecB|)r=m.vq.B

r=(mxx1.05xx10^5)/(1.60xx 10^-19xx0.75)r=m×1.05×1051.60×1019×0.75

r=mxx8.75xx10^23r=m×8.75×1023

  1. For "U"235U235:
    r_235=3.9xx10^-25xx8.75xx10^23r235=3.9×1025×8.75×1023
    =0.34125m=0.34125m
  2. For "U"238U238:
    r_238=3.95xx10^-25xx8.75xx10^23r238=3.95×1025×8.75×1023
    =0.345625m=0.345625m

Distance between the two isotopes is equal to difference between the two diameters

![http://buphy.bu.edu](https://useruploads.socratic.org/Rb5WBK3TUigbNrCklF3B_12a.GIF)
=2xx(0.345625-0.34125)=0.00875m=2×(0.3456250.34125)=0.00875m
=0.875cm=0.875cm