QQS: why is metal shiny?
nothing grabs your eye quite like shiny and when it comes to shine,
nothing beats good metallic sheen from mirrors to jewelry.
Medals are prized for their ability to glitter like well gold.
Their shininess is basically a built inproperty and there’s a good reason
why it’s a quirk of the weird way their electron behavior.
In a metal atom the outermost electrons are only weakly attached to the nucleus.
When a bunch of metal atoms come together in a chunk,
these outer electrons wiggle free creating what scientists usually think
of as a negatively charged sea of electrons flowing around a network of
positively charged ions.
This moving sea is a big part of what makes metals metal.
For example you can hammer them into different shapes without cracking them
because the electrons can move to compensate for the atomic nuclei
shifting around and all those free electrons are great at conducting electricity
that’s also why metals are shiny. What we call shine is actually reflected light
but it doesn’t just bounce off the surface like a tennis ball.
Instead when a wave of light hits the sea of electrons the electrons
absorb the light waves energy which makes them wobble a little
that movement generates a second wave of light, one that radiates back up from the surface
that’s what we see is a shine.
The free electrons and metals are especially good at this vibrating to match visible light thing
but deferent metals shine in different ways. That’s big as dependingon the metal.
The sea of electrons will have a different mass and density which affects how freely the electrons can
move and therefore whether they can vibrate to match the incoming wave.
Most metals are silvery because they reflect most visible light but
not all of it which makes them a little darker than pure white. A few metals like gold and
copper aren’t able to reflect the bluest wavelengths of light so they shine with
a reddish or yellowish hue
and there are no guarantees that a metal will reflect higher energy waves like UV and x-rays at all.
Waves are reflected penetrate into the metal
can easily be absorbed or pass on through depending on both the type of metal and how thick it is.
Silver for example is one of the best reflectors of visible light which is why it was one of the
first metals used for mirrors but it’s terrible at reflecting UV rays
If i locked you in a thin silver box and put it in direct sunlight it would be
completely dark in there but you could still get sunburned, you know,
hypothetically. Metals like tin and aluminum are much better at reflecting
ultraviolet light which is why they’re used in roofing.
Lead on the other hand can reflect even the high-energy x-rays that penetrate most metals making it an
ideal way to protect parts of your body that your doctor doesn’t want x-ray.
That’s also why Superman can’t see through it. So metals can shine in lots of different ways
but it all comes from the same thing, a bunch of electrons moving around.
感谢提问 尤其感谢赞助商对patreon的支持 patreon一直致力于回答这些提问
Thanks for asking and thanks especially to all of our patronson patreon who keep these answers coming.
If you would like to submit questions to be answered you can go to patreon.com/scishow