Verified Solution • 2025–26 Session moderate

QJEEM21Ph251b: JEE Main 2021 Physics - Class 12 JEEM21Ph251b Solution: Two ions having same mass have charges in the ratio 1 : 2. They …

Two ions having same mass have charges in the ratio 1 : 2. They are projected normally in a uniform magnetic field with their speeds in the ratio 2 : 3. The ratio of the radii of their circular trajectories is :

Multiple Choice Options

  • A 1:04
  • B 4:03
  • C 3:01
  • D 2:03

Step-by-Step Verified Solution

R=mvqB⇒R1R2=mv1q1Bmv2q2B=v1q1×q2v2=q2q1×v1v2R = {{mv} \over {qB}} \Rightarrow {{{R_1}} \over {{R_2}}} = {{{{m{v_1}} \over {{q_1}B}}} \over {{{m{v_2}} \over {{q_2}B}}}} = {{{v_1}} \over {{q_1}}} \times {{{q_2}} \over {{v_2}}} = {{{q_2}} \over {{q_1}}} \times {{{v_1}} \over {{v_2}}}

=21×(23)=43= {2 \over 1} \times \left( {{2 \over 3}} \right) = {4 \over 3}

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