Reflection like paint

The other day, my daughter and I found an interesting rainbow on the side of our house.At first, I wondered if it was too thick and painted. Why a rainbow here? I was curious and looked at it seriously, and my daughter came up to me.Then, my daughter stood on the backlight, and the rainbow disappeared in her shadow.I had been completely convinced that the rainbow was painted until that moment, and I was astonished to see it suddenly disappear.Why did it disappear? I thought, "But it was not paint, it was light.You know, those reflector-like sparkles you often see on bicycle wheels.From that little sparkle, such an intense rainbow is born.

It was the moment when my image of light changed completely.