(c) Potential energy=$\frac{1}{2}m\omega^{2}y^{2} = \frac{1}{4} \times \frac{1}{2}m\omega^{2}a^{2}$ $y^{2} = \frac{a^{2}}{4} \Rightarrow y = \pm \frac{a}{2}$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.