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A particle of mass $\mathrm{m}$ and charge $\mathrm{q}$ moving with velocity $\mathrm{v}$ enters region-b form region-a along the normal to the boundary as shown is the figure. Region-b has a uniform magnetic field $B$ perpendicular to the plane of the paper. Also, region-b has length L. Choose the correct statements :
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The correct answers are:
The particle enters region-c only if $\mathrm{v}>\frac{\mathrm{qLB}}{\mathrm{m}}$, Path of the particle is a circle in region-b, Time spent in region -b is independent of velocity v
Particle enter region 'c' if
Radius is greater than ' $L$ ' $\Rightarrow \frac{m V}{q B}>L \Rightarrow V>\frac{q B L}{m}$
$\because$ B is uniform and $\overrightarrow{\mathrm{V}} \perp \overrightarrow{\mathrm{B}}$ so.
Path is circular in region b
$$
\text { Time spent }=\frac{\text { Angle cov ered }}{\omega} \quad \omega=\frac{\mathrm{qB}}{\mathrm{m}}
$$
Now angle covered depens on whether particle goes to region c or comes back to region 'a'
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