Question

How does heat- reflective glass reflect only heat and pass light?
I read that it is done by simply reflecting ultraviolet and infrared rays.. But still i need some explanation on how does it reflect only ultraviolet and infrared, allowing all visible light to pass through?

Answer 1

i'm not sure but maybe it has something to do with fact that we cant see infrared rays (light) and if we saw ultraviolet rays (light) it would probably make us blind because its too strong.

Answer 2

I am asking "How is the glass able to reflect ultraviolet and infrared and allow only visible light to pass though?"

Answer 3

Why would you expect any material to be transparent to all wavelengths of light? All materials, including glass, have an absorption that varies with wavelength:

http://www.sinclairmfg.com/datasheets/optical3.html

The reason is simply that various coupled vibrations of atoms and bonds in the material have the right frequency to absorb photons of a given wavelength, and will. The only time a material is ever transparent at a given wavelength is if there are NO possible vibration modes that can be excited by a photon of that energy. It's asking for a lot for that to be true for ALL wavelengths -- in fact, it's impossible. You're bound to hit a wavelength that excites some transition or other.

The trick to making a material that blocks some wavelengths but lets others in is to tune the kind of excitations that are possible in the material.

Answer 4

If a transition is possible by infrared wave, then i guess that transition should also be possible by visible light (it has more energy than infrared).. So, if infrared is blocked, shouldn't visible light also be blocked?

Answer 5

Heavens no. This is exactly the distinction produced by quantum mechanics. Classically, yes, if a transition is possible by IR then visible light should excite it, too. But quantum mechanically, no. A transition is only excited by EXACTLY the right wavelength photon, no more, no less. A transition triggered by an IR photon will not respond at all to both lower energy photons (microwave) or higher energy photons (visible).

Answer 6

@Carl_Pham What about compton effect where 'part of the energy' of the photon is transferred to the scattering electron?
In compton effect all energy is not transferred!

Answer 7

@ujjwal DO YOU KNOW HOW THESE GLASSES ARE MADE??????

Answer 8

Not much... But i know a thin (really thin) metallic coating of some metal (which i can't recall now) is coated on its surface!
I didn't find much information on internet.. maybe because such glasses are not much used currently!

Answer 9

nope they r used a lot everywhere:)
http://www.explainthatstuff.com/how-low-e-heat-reflective-windows-work.html
read this your all questions get cleared:)

Answer 10

I have already read it all.. Things are explained from layman point of view and there isn't much scientific explanation about how it actually works..

They have described what it does but not how it does!

I got to know about that metal coating thing from that link only.. And yeah the coatings are of titanium dioxide, bronze, silver, or stainless steel..
The thin air column filled with argon in between would do nothing to prevent ultraviolet or infrared rays from passing through..
And i don't know how would metal coating do that..

And yeah if it blocks infrared, it should probably make some change to visible light too as suggested in compton effect (some part of energy is transmitted)

Please correct me if i am wrong in understanding compton effect!

Answer 11

metal coating how it works u want to know and yes you get it wrong with compton effect:)

Answer 12

@ujjwal, we are talking about bound states, not free electrons.

Answer 13

I had half-guessed i was wrong at that point but i was not certain! Thanks @Carl_Pham