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Mirrors and reflections

by tom12519
Tags: mirrors, reflections
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tom12519
#1
Oct27-07, 04:58 PM
P: 5
I have been pondering for a while upon how mirrors and reflections work. In a standard shiny metal, metallic bonding allows electrons to be free of atoms and thus occupy any energy level. This means that electrons can absorb the photon and re-emit it as the same frequency. However, I still do not understand how a non-metallic surface (for example a thin sheet of plastic at a very low angle) can reflect light as well as how gold manages to reflect light but also have a gold colour apparently added to the light simultaneously.

Any responses/references to reading material would be greatly appreciated.
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Claude Bile
#2
Oct28-07, 08:13 PM
Sci Advisor
P: 1,472
Quote Quote by tom12519 View Post
I have been pondering for a while upon how mirrors and reflections work. In a standard shiny metal, metallic bonding allows electrons to be free of atoms and thus occupy any energy level. This means that electrons can absorb the photon and re-emit it as the same frequency. However, I still do not understand how a non-metallic surface (for example a thin sheet of plastic at a very low angle) can reflect light as well as how gold manages to reflect light but also have a gold colour apparently added to the light simultaneously.

Any responses/references to reading material would be greatly appreciated.
The highlighted section is incorrect, specular reflection is due to the response of atoms on a surface excited by an EM wave and is a non-resonant process. In other words, you need to think of the atoms acting as little antennae, rather than bound electrons jumping up and down energy levels.

Claude.
minorwork
#3
Oct29-07, 03:51 AM
P: 203
I believe that gold reflects infrared better than does aluminum. This is why the solar reflectors on space suit helmet lenses are covered by a thin layer of gold. This does offer increased efficiency for a solar power reflecting device.

pixel01
#4
Oct29-07, 10:19 AM
P: 691
Mirrors and reflections

Quote Quote by minorwork View Post
I believe that gold reflects infrared better than does aluminum. This is why the solar reflectors on space suit helmet lenses are covered by a thin layer of gold. This does offer increased efficiency for a solar power reflecting device.
Is it something to do with the softness of gold?. Gold is easily made to very thin plates.
minorwork
#5
Oct29-07, 10:59 AM
P: 203
I couldn't say why. Around the gas crunch in the early 70s I was building reflector molds and the Physics and Chemistry Handbook showed gold reflecting better. Right now I don't know where the wife has hid it. Gold is the most malleable of metals. Pretty dense too.

Mirrors mess me up anyway. Why do they reverse right and left and not up and down?
pixel01
#6
Oct29-07, 11:38 AM
P: 691
Quote Quote by minorwork View Post
I couldn't say why. Around the gas crunch in the early 70s I was building reflector molds and the Physics and Chemistry Handbook showed gold reflecting better. Right now I don't know where the wife has hid it. Gold is the most malleable of metals. Pretty dense too.

Mirrors mess me up anyway. Why do they reverse right and left and not up and down?
I am still very confused about reflection property of metal and other material. Why only very smooth surfaces reflect better?, why graphit doesn't reflect well? etc..
As for your question of mirror : left-right and up-down, it only because the mirror turn your image 180 degrees compared to you. When you turn, your up is still up, down is still down, but your left turn to right and vice versa.
minorwork
#7
Oct29-07, 07:17 PM
P: 203
You are right. I looked some stuff up and a mirror reverses symmetry. Humans are bi-
lateral symmetric. That is we are not symmetric top and bottom. Thought I saw a similar question to yours somewhere on this site with a pretty good explanation. If I find it I'll mention it.
Griff38
#8
Nov1-07, 03:44 AM
P: 8
Mirrors show lateral inversion because of the fact that the distance the image is behind the mirror is the same as the object is infront so think of a letter F infront of a mirror, pick some points on the letter F to the left of the mirror and think where their image would appear to be in the mirror then join these point up to reconstruct the letter and you will see it have been left to right reversed.

F ¦


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