The energy of a wave can be calculated using the equation E = hf, where E is energy, h is Planck's constant (6.62607015 x 10^-34 J.s) and f is frequency.
For a 3.12 x 10^18 Hz wave, the energy can be calculated as:
E = h * f
E = (6.62607015 x 10^-34 J.s) * (3.12 x 10^18 Hz)
E = 2.06 x 10^-15 J
So, the energy of a 3.12 x 10^18 Hz wave is approximately 2.06 x 10^-15 joules.