Science Quiz
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The Last Conformist
Irresistibly Attractive
If you're not going to accept my answer, I'd like to see it shot down.
betazed
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Ooops.
I am sorry I did not see your answer at all since it was at the bottom of the page and all. I did not mean to ignore it. Anyway, you say
I am slightly confused. You have to expand your answer a bit. Who does not absorb the incoming photons and reemits new ones?
The Last Conformist
Irresistibly Attractive
Well, everything absorbs incoming photons and reemits new ones. That mirrors appear to reflect incoming rays is because the new photons are emited in a coherent way that preserves the "picture", while most surfaces reemit so-to-speak chaotically, causing the impression of a coloured surface.
(Of course, in either case some of the incoming effect won't be reemited immediately, but go to warming up the object, driving termal radiation.)
(Of course, in either case some of the incoming effect won't be reemited immediately, but go to warming up the object, driving termal radiation.)
Pirate
Emperor
Alright, to keep this thread alive I'll take a guess.
In order for a lattice of molecules to affect the propogation of a light wave, the spacing of the molecules has to be on the order of the wavelength of the light. Glass is an amorphous solid, with no regular structure. The gaps and spaces are random and do not affect light in a coherent way (?). A reflective material is smooth and has a regular molecular structure in which atoms are spaced at about the wavelength of visible light so they reflect the wave?
In order for a lattice of molecules to affect the propogation of a light wave, the spacing of the molecules has to be on the order of the wavelength of the light. Glass is an amorphous solid, with no regular structure. The gaps and spaces are random and do not affect light in a coherent way (?). A reflective material is smooth and has a regular molecular structure in which atoms are spaced at about the wavelength of visible light so they reflect the wave?
betazed
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I guess all of you were close. Here is the answer straight from sciam.
"
The oscillating electrical field in the incoming light wave produces a force on the charges inside the mirror. Most of the charges are either too heavy (as is true for the nuclei of the atoms) or too tightly bound (as is true for most of the electrons) to vibrate significantly in response to this field. The comparatively loosely held bonding electrons, along with the free electrons present in metals, can move in response to these electrical forces, however. These electrons oscillate at the same frequency as the incident light, which gives rise to the reflected wave.
Because there are a great many electrons in the mirror, all vibrating at the frequency of the incident light, reflection from the mirror is really a group effort. All the electrons dance to the same music, whose rhythm is provided by the incident light wave. This coordination causes the reflected wave to make the same angle with respect to the mirror's surface as does the incident beam.
A typical mirror consists of a piece of glass that has been coated with a layer of metal. Glass by itself reflects a little of the light, but the metal layer greatly boosts the reflectivity. If the metal were perfectly conducting, it would reflect all of the light, but the conductivity of real metals is less than perfect. This imperfection leads to some absorption of light in the metal. A polished silver surface, for example, reflects about 93 percent of the incident visible light, which is very good as metals go. Interestingly, if the metal layer is very thin--only a few hundred atoms thick--then much of the light leaks through the metal and comes out the back. If you get the thickness of a metal layer right, you can make a beam splitter that divides an incident beam of light into two equal parts, with just a little bit of the light lost to the metal film itself.
As good as the reflectivity of a silver mirror is, you can do much better with dielectric mirrors. These reflectors consist of alternating layers of two transparent materials that have different indices of refraction. Dielectric mirrors can have reflectivities of 99.999 percent or better at the wavelength for which they are designed. In these mirrors, essentially all of the incident light reflects, and virtually none is absorbed in the mirror or transmitted through it.
"
"
The oscillating electrical field in the incoming light wave produces a force on the charges inside the mirror. Most of the charges are either too heavy (as is true for the nuclei of the atoms) or too tightly bound (as is true for most of the electrons) to vibrate significantly in response to this field. The comparatively loosely held bonding electrons, along with the free electrons present in metals, can move in response to these electrical forces, however. These electrons oscillate at the same frequency as the incident light, which gives rise to the reflected wave.
Because there are a great many electrons in the mirror, all vibrating at the frequency of the incident light, reflection from the mirror is really a group effort. All the electrons dance to the same music, whose rhythm is provided by the incident light wave. This coordination causes the reflected wave to make the same angle with respect to the mirror's surface as does the incident beam.
A typical mirror consists of a piece of glass that has been coated with a layer of metal. Glass by itself reflects a little of the light, but the metal layer greatly boosts the reflectivity. If the metal were perfectly conducting, it would reflect all of the light, but the conductivity of real metals is less than perfect. This imperfection leads to some absorption of light in the metal. A polished silver surface, for example, reflects about 93 percent of the incident visible light, which is very good as metals go. Interestingly, if the metal layer is very thin--only a few hundred atoms thick--then much of the light leaks through the metal and comes out the back. If you get the thickness of a metal layer right, you can make a beam splitter that divides an incident beam of light into two equal parts, with just a little bit of the light lost to the metal film itself.
As good as the reflectivity of a silver mirror is, you can do much better with dielectric mirrors. These reflectors consist of alternating layers of two transparent materials that have different indices of refraction. Dielectric mirrors can have reflectivities of 99.999 percent or better at the wavelength for which they are designed. In these mirrors, essentially all of the incident light reflects, and virtually none is absorbed in the mirror or transmitted through it.
"
RoddyVR
Veteran Board NESer
i assume if someone had looked it up they could have gotten those 3 paragraphs. but expecting them as an answer from people who should NOT be looking it up online is a bit much i think.
not exactly sure who's turn it is, but this thread doesnt seem to be keeping to that "whoever answers right gets to ask" rule anyway. so:
why doesnt a ballpoint pen work in space (or upside down)?
not exactly sure who's turn it is, but this thread doesnt seem to be keeping to that "whoever answers right gets to ask" rule anyway. so:
why doesnt a ballpoint pen work in space (or upside down)?
betazed
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I was not looking for all those details at all. All I was looking for was the key features of glass and metal that makes a mirror a mirror.
The reason why glass is transparent and metals are reflective is because of the free electrons in them. That was all I was looking for.
I just quoted the sciam answer to be complete and I was being lazy and did not want to type the answer myself.
The_Unforgiven
KoEkWaUs
Lack of gravity, resp, gravity in wrong direction
RoddyVR
Veteran Board NESer
oh come on....
i guess i should have been a little more specific, but your answer is almost implied in the question.
i guess it should have been more "why do ballpoint pens need gravity (in the right direction)?"
The_Unforgiven
KoEkWaUs
To win the fierce battle against the adhesion and surface tension forces holding the ink back
RoddyVR
Veteran Board NESer
ok. then YOU ask one 
The_Unforgiven
KoEkWaUs
Everybody knows a bending straw right?
Position it so that it looks like a capital L
If I blow in it from above, it bends in the direction opposite to the short end.
If I suck on it, what does it od and WHY?
Position it so that it looks like a capital L
If I blow in it from above, it bends in the direction opposite to the short end.
If I suck on it, what does it od and WHY?
The_Unforgiven
KoEkWaUs
nobody? if you want me to elaborate, tell me
The Last Conformist
Irresistibly Attractive
Not the slightest idea what a bending straw is.
The_Unforgiven
KoEkWaUs
Don't know waht the correct term is... Toy drink through it. And it can bend at about 1/4 of its length
Bozo Erectus
Master Baker
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Why Lord why? Why do they tempt me so?
(looks sternly at fingers: Im warning you, dont you dare type that! )
RoddyVR
Veteran Board NESer
if i understand correcly then you're saying that if you blow into your "L" shaped straw it will move left.
and teh question is what will happen if you suck on it instead.
i'd say it will move right.
cause you sucking on the straw will create a less dense atmosphere to the right of the "exit" and the straw will move there to fill the void (along with the air around it).
this is ofcourse assuming that while sucking (or blowing) into the straw, you're not realy holding it with anything (including your lips) cause in that case nothing will happen other then your lungs filling up.
and teh question is what will happen if you suck on it instead.
i'd say it will move right.
cause you sucking on the straw will create a less dense atmosphere to the right of the "exit" and the straw will move there to fill the void (along with the air around it).
this is ofcourse assuming that while sucking (or blowing) into the straw, you're not realy holding it with anything (including your lips) cause in that case nothing will happen other then your lungs filling up.
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