(d) $l = \frac{FL}{AY}\therefore l \propto \frac{1}{r^{2}}\lbrack F,L\ $and$\ Y$ are constant] $\frac{l_{1}}{l_{2}} = \left( \frac{r_{2}}{r_{1}} \right)^{2} = (2)^{2} = 4$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.