JEE Advanced 2013 · Paper 1, Physics question 13

A particle of mass $M$ and positive charge $Q$, moving with a constant velocity $\vec u_1=4\hat i\ \mathrm{m\,s^{-1}}$, enters a region of uniform static magnetic field normal to the $x$-$y$ plane. The region of the magnetic field extends from $x=0$ to $x=L$ for all values of $y$. After passing through this region, the particle emerges on the other side after 10 milliseconds with a velocity $\vec u_2=2\left(\sqrt3\hat i+\hat j\right)\ \mathrm{m\,s^{-1}}$. The correct statement(s) is (are)