Why do white objects reflect light back compared to black objects?

Question

Why do white things reflect light back, while black absorbs it? Don't just repeat my question if you know what I mean, I'm asking WHY.

Answer 1

You can look at atoms and molecules as oscillating systems with their own oscillating frequency. Light is electromagnetic wave it start shaking or "oscillators". If "oscillator" frequency close to frequency of the light we have resonance and all energy of the light is converted into oscillation energy. If frequencies are far apart, energy of the light is conserved and ligh can either pass through the material or reflect.
So if atoms and molecules of the object do not have resonance frequencies close to the visible light frequencies you will see white color. If on the contrary the range of frequencies coinside with visible light frequencies you will se black color. If only part of the spectrum, then you will see colored object.

Answer 2

It is a matter of color really. White light as we know is made of the colors of the Rainbow. (ROYGBIV).

the color light is reflected, and the excess are absorbed, this giving us our color.

White Color absorbs all light.

While black color absorbs all white light, and appears black.