Why are the green traces thick at the peaks of the cycle? What causes this ‘roughness’ in the oscilloscope reading?
Roughness means some variations of signal:
 1. High frequency additive oscillations (or noise). Try using much lower time/div to see them. Try to limit input bandwidth to suppress them.
 2. Low frequency addidive oscillations or amplitude modulation. Try using much higher time/div. Also, try single-shot trigger mode to suppress multiple waveform accumulation on the screen.