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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 radii of their circular trajectories is

Asked in JEE Main 25th July 2nd Shift 2021 · Circular motion: radius, period and energy

• (1) 2:3
• (2) 1:4
• (3) 3:1
• (4) 4:3

Step-by-step solution

Why the other options are wrong

• (1) Uses only the speed ratio and ignores the charges.
• (2) Squares the charge ratio and ignores the speeds.
• (3) Puts speed in the denominator, using r ∝ 1/(qv).

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