A proton is projected with a speed of $2 \times 10^{6}(\mathrm{~m} /
\mathrm{s})\( at an angle of \)60^{\circ}\( to the \)\mathrm{X}$ -axis. If a
uniform mag. field of \(0.104\) tesla is applied along \(\mathrm{Y}\) -axis, the
path of proton is
(a) A circle of \(\mathrm{r}=0.2 \mathrm{~m}\) and time period $\pi \times
10^{-7} \mathrm{sec}$
(b) A circle of \(\mathrm{r}=0.1 \mathrm{~m}\) and time period $2 \pi \times
10^{-7} \mathrm{sec}$
(c) A helix of \(r=0.1 \mathrm{~m}\) and time period $2 \pi \times 10^{-7}
\mathrm{sec}$
(d) A helix of \(\mathrm{r}=0.2 \mathrm{~m}\) and time period $4 \pi \times
10^{-7} \mathrm{sec}$