0
$\begingroup$

I read that a (sufficiently) white surface reflects more (visible) light than a mirror. Is that true? And if yes, why?

$\endgroup$
9
  • 2
    $\begingroup$ "A mirror" and "a white surface" are not opposites. You could argue that a mirror is also a white surface - just a white surface that happens to reflect specularly (parallel rays). $\endgroup$ – Steeven Apr 16 at 10:09
  • $\begingroup$ Interesting perspective. $\endgroup$ – Raffael Apr 16 at 10:13
  • 1
    $\begingroup$ To develop the first comment a bit more, you can consider the following thought experiment: Start with a mirror made of a homogeneous material, say stainless steel for instance, then break it into pieces again and again a couple of times, each fragment will reflect light as efficiently as the the initial mirror (albeit in a different direction). If you do this a large enough amount of time, you end up with a white powder, whose reflecting power is the same as the one of the initial mirror (only spread over a large amount of grains). $\endgroup$ – Serge Hulne Apr 16 at 12:30
  • $\begingroup$ Hi, please provide the reference which made that statement. It would be helpful to us, as then we could show what assumptions it made about a mirror's reflectivity $\endgroup$ – Carl Witthoft Apr 16 at 14:06
  • $\begingroup$ Here’s one possible example: patentimages.storage.googleapis.com/c7/70/db/6a3db1bed0860d/… $\endgroup$ – Serge Hulne Apr 16 at 15:21
6
$\begingroup$

Have you ever wondered why things show colour? Well when light is incident on a surface, light of certain wavelengths are absorbed and we see the complement colours.For example a green surface absorbs light of all colours other than green. But a white surface is a surface that reflects out light of all wavelengths unlike a black surface which absorbs all light.

Now imagine shining a green laser at a mirror . What we get is a reflected green beam.if we repeat this experiment for all other 6 colours we will get similar results.So we can conclude that a mirror reflects light of all colours just like a white surface .

So what makes a mirror different from a white surface?

A mirror possesses specularity i.e parallel rays are reflected parallel to each other thus maintaining an image which does not happen for all white surfaces. A surface which is not a mirror does not reflect the parallel rays in a specular fashion so the reflected rays mix into one homogeneous white light without producing image.

So basically if I take a white surface and give it the property of specularity I get a mirror.

Typically how much light is reflected depends on the surface.For example if you take a sufficiently white surface it will reflect 100 % light but if you compare it with a household mirror that reflects only 80% light then the white surface would reflect more than the mirror.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.