Physics - Magnetism Question with Solution | TestHub

Ans (A,B)

If q > 0 : $\theta =60^{\circ }$

At $t=\frac{1}{6}\cdot \frac{2\pi m}{qB}$, $t=\frac{\pi m}{3qB}$

Hence particle will enter region I from II for first time at $t=\frac{\pi m}{3qB}$. Option (A) is correct, option (C) is incorrect.

Case (2) q < 0 : $R=\frac{m{V}_0}{qB}$, $t=\frac{1}{4}\cdot \frac{2\pi m}{|q|B}=\frac{\pi m}{2|q|B}$. Hence option (B) is correct.