When we see an object as white, it means that the object reflects all the colors of the visible spectrum equally. In other words, white light is composed of a combination of different colors (wavelengths) of light, including red, orange, yellow, green, blue, indigo, and violet. When white light falls on an object, that object appears white because it reflects all the colors present in the incident light.
On the other hand, if an object appears to have a specific color, such as a red apple, it means that the object selectively absorbs certain colors of light and reflects the color we perceive. In the case of the red apple, it absorbs most of the colors in the visible spectrum but reflects predominantly red light.
For an object to appear white, it must have the ability to reflect all the colors equally. This can occur if the object's surface or material has properties that allow it to reflect a broad range of wavelengths across the visible spectrum without significant absorption. Materials that possess this property are known as "white" or "colorless" materials.
It's important to note that the perceived color of an object depends on the light that is reflected from its surface. If an object does not reflect any light, it will appear black since there is no light reaching our eyes to be detected.