If light bounces off objects multiple times and a part of the visible light is absorbed, why is a white wall still white when the light has already been partially absorbed by other objects and no pure white light is being transmitted further?
Why do objects not appear more colorful or in the “wrong” color, if the rooms is filled with different objects, considering that white light should become less white with each bounce as light is partially absorbed?
In: Physics
Your eyes and brain automatically adjust for the “white balance” in a room, so you can understand the true color of objects even though the light is not perfect.
Cameras do this too, but if you take a lot of pictures in different settings with different cameras or phones, you will find that cameras do not all do this the same, and some are better than others.
If the light is extremely far from pure white, you will eventually have a hard time canceling out the effect and perceiving the true color of things. For example if the light in a room is only yellow, it would be hard to tell a white object apart from a yellow object because they will be both reflect all the light. And it would be hard to tell a blue object apart from a black object because they both reflect none of the yellow light. Old sodium gas street lamps produced light like this so you may have experienced it, and you can also experiment with newer color-changing LED lights to see a similar effect. As long as there is enough mixture of colors for items to reflect them differently, your brain will try to make sense of it and understand what color those items actually are. Eventually, you will lose that ability as the light becomes too monochromatic to show any differences beyond light vs dark.
The light source in the room (presumably white) will always give out much more light than any object just reflecting a small part of this light source. Hence why white objects will still look predominantly white.
But if you bring a colored object close to a white surface, you’ll definitely start to see some coloration on the white surface.
Normally, objects reflect only a small fraction if the light source. This means that the majority of light hitting your white wall will be directly from the source. Any other coloration is usually too minor to notice.
There are situations where it may become apparent. I used to have a safety orange workout shirt and whenever the sun hit me while I was in the car, the entire interior turned a blazing orange.
This happened because the sun wasn’t shining on most of the inside of the car, so the main light source *was* the shirt, and it was very bright so it reflected a lot of light.
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