eli5: What is the difference between a mirror and a white object?

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I mean, what does a white object do? Absorbs nothing, reflects all light back.

What does a mirror do? Absorbs nothing, reflects all light back.

Having the same characteristics, how does a mirror reflect an image and a white object, a white texture?

In: Physics

18 Answers

Anonymous 0 Comments

>Having the same characteristics

False premise.

A mirror has, well, a mirror finish. This means that on a very tiny scale(microscopic), it is still relatively flat and smooth. When something is sufficiently smooth, you will see an even reflection as all light bounces off in the same direction.

On that same scale, a white non-reflective object, is jagged and irregular. This scatters light in all directions.

A good easy to google example of this are modern gravestones. [The exact same material with different finishes in different places.](https://www.whiteman-monumental.co.nz/images/headstone-finishes-7.jpg)

Some polished very smooth, some left very rough.

Edit: It begins to get even more interesting when things are regularly jagged on a microscopic scale. That’s where you get things like reflective tape or coatings on safety clothing, road signs, etc. Sometimes it is small spheres which insure there’s nearly always a ray of light that bounces directly back, other times it is geometric shapes that bounce a light twice so it comes right back out the same way it went in, like in vehicle lights.(imagine the inside of a hollow box all being mirrors)

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