(c) $e^{2} = \frac{a^{2} - b^{2}}{a^{2}}$ and ${e'}^{2} = \frac{b^{2} - a^{2}}{b^{2}}$ $\Rightarrow \frac{1}{e^{2}} + \frac{1}{{e'}^{2}} = 1$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.