Verified Solution • 2025–26 Session moderate

QJEEM21Phf658: JEE Main 2021 Physics - Class 12 JEEM21Phf658 Solution: Two ions of masses 4 amu and 16 amu have charges +2e and +3e…

Two ions of masses 4 amu and 16 amu have charges +2e and +3e respectively. These ions pass through the region of constant perpendicular magnetic field. The kinetic energy of both ions is same. Then :

Multiple Choice Options

  • A lighter ion will be deflected less than heavier ion
  • B lighter ion will be deflected more than heavier ion
  • C both ions will be deflected equally
  • D no ion will be deflected

Step-by-Step Verified Solution

r=PqB=2mkqBr = {P \over {qB}} = {{\sqrt {2mk} } \over {qB}}

Given they have same kinetic energy

r∝mqr \propto {{\sqrt m } \over q}

r1r2=42×316=34{{{r_1}} \over {{r_2}}} = {{\sqrt 4 } \over 2} \times {3 \over {\sqrt {16} }} = {3 \over 4}

r2=4r13{r_2} = {{4{r_1}} \over 3} (r2 is for heavier ion and and r1 is for lighter ion)

JEE Main 2021 (Online) 27th August Morning Shift Physics - Magnetic Effect of Current Question 109 English Explanation
sin⁡θ=dR\sin \theta = {d \over R}

θ\theta →\to Deflection

θ∝1R\theta \propto {1 \over R}

(R →\to Radius of path)

∵\because R2 > R1 ⇒\Rightarrow θ\theta 2 < θ\theta 1

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