(c) $n = \frac{1}{2\pi}\sqrt{\frac{k}{m}} \Rightarrow n \propto \frac{1}{\sqrt{m}} \Rightarrow \frac{n_{1}}{n_{2}} = \sqrt{\frac{m_{2}}{m_{1}}}$ $\Rightarrow \frac{n}{n_{2}} = \sqrt{\frac{4m}{m}} \Rightarrow n_{2} = \frac{n}{2}$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.