

Potential Energy = PE = ½ m ω2y2
Total Energy = T = ½ m ω2 a2
Given condition is that PE = ½ T
Hence, ½ m ω2y2 = ½ * ½ m ω2a2
which gives y2 = ½ a2
y = a/√2
Hence, the displacement should be = a/√2 for which potential energy is half of the maximum energy of the oscillator
