For  $B=\frac{8}{13} \frac{p}{QR},$ radius of path

$R^{\text{'}}=\frac{p}{O.B}=\frac{p\times 13QR}{Q8p}=\frac{13}{8}R$

Using pythagorous theorem,$y=\frac{5R}{8}$

$\therefore$    particle will enter region 3 through point  $P_2$ for $B>\frac{2}{3}\frac{p}{QR}$

Radius of path $<\frac{3PQR}{Q2p}=\frac{3}{2}R$

$\therefore$    Particle will not enter in region 3 and will re-enter region 1

Charge on momentum $= \sqrt{2}p.$ When particle enters region 1 between entry point and farthest point from y-axis.