POV-Ray : Newsgroups : povray.advanced-users : A question of physics Server Time
29 Jul 2024 08:19:02 EDT (-0400)
  A question of physics (Message 7 to 16 of 36)  
<<< Previous 6 Messages Goto Latest 10 Messages Next 10 Messages >>>
From: Andrew Coppin
Subject: Re: A question of physics
Date: 8 May 2003 03:49:40
Message: <3eba0c14$1@news.povray.org>
OK, well, a lump of shashed up ice doesn't look reflective at all... but
take a bit and polish it to give it a nice smooth surface and you find that
it actually IS reflective. Was thinking, if you have a layer of gas, it's
surface probably isn't smooth, which might explain why it doesn't look
reflective.

If that makes sense.

Andrew.


Post a reply to this message

From: ABX
Subject: Re: A question of physics
Date: 8 May 2003 03:58:36
Message: <233kbv4bikb70rgnc9k1cso1a1kdqicgh8@4ax.com>
On Thu, 8 May 2003 08:48:09 +0100, "Andrew Coppin" <orp### [at] btinternetcom> wrote:
> OK, well, a lump of shashed up ice doesn't look reflective at all...

But I think it is reflective, just with a lot of blur :-)

> Was thinking, if you have a layer of gas, it's
> surface probably isn't smooth, which might explain why it doesn't look
> reflective.

On desert you can see images in the air. You know how ?
http://www.islandnet.com/~see/weather/graphics/photos/supmirag.gif

ABX


Post a reply to this message

From: Warp
Subject: Re: A question of physics
Date: 8 May 2003 06:17:03
Message: <3eba2e9f@news.povray.org>
Andrew <ast### [at] hotmailcom> wrote:
> If something was truly non-reflective,
> it would be perfectly invisible

  A transparent object which refracts light is never invisible.

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -


Post a reply to this message

From: Christoph Hormann
Subject: Re: A question of physics
Date: 8 May 2003 06:34:53
Message: <3EBA32CD.AF03425E@schunter.etc.tu-bs.de>
Andrew Coppin wrote:
> 
> Here's a simple enough question...
> 
> Is it possible for a transparent substance to be non-reflective? Or are all
> transparent substances inherantly reflective to a certain degree?

Reflection is an inherent effect on all interfaces between materials of
different optical density (i.e. ior, speed of light in the material)

The amount of reflection depending on the incident angle and the materials
can be calculated with the fresnel equations.  This works for both a
transit from less dense to more dense medium as well as the other way
round.  More information can be found in the links from:

http://www-public.tu-bs.de:8080/~y0013390/pov/water/water_app1.html#reflect

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 28 Feb. 2003 _____./\/^>_*_<^\/\.______


Post a reply to this message

From: sascha
Subject: Re: A question of physics
Date: 8 May 2003 08:03:38
Message: <3eba479a@news.povray.org>
At school a teacher told us that reflection is caused if the surface is 
electroconductive (at the frequency of the light-wave). In that case it 
will "short-circuit" the "electric part" of the wave (light is an 
electromagnetic-wave) - because the electric and the magnetic vectors 
are perpendicular the angle of reflection is equal to the angle of 
incidence.

I have got no idea if this is true - could be complete nonsense...

-sascha


Christoph Hormann wrote:
> 
> Andrew Coppin wrote:
> 
>>Here's a simple enough question...
>>
>>Is it possible for a transparent substance to be non-reflective? Or are all
>>transparent substances inherantly reflective to a certain degree?
> 
> 
> Reflection is an inherent effect on all interfaces between materials of
> different optical density (i.e. ior, speed of light in the material)
> 
> The amount of reflection depending on the incident angle and the materials
> can be calculated with the fresnel equations.  This works for both a
> transit from less dense to more dense medium as well as the other way
> round.  More information can be found in the links from:
> 
> http://www-public.tu-bs.de:8080/~y0013390/pov/water/water_app1.html#reflect
> 
> Christoph
>


Post a reply to this message

From: Andrew Coppin
Subject: Re: A question of physics
Date: 8 May 2003 16:56:25
Message: <3ebac479$1@news.povray.org>
>   A transparent object which refracts light is never invisible.

...unless it's an even-thickness slab, viewed exactly square-on *grin*

Andrew.


Post a reply to this message

From: Andrew Coppin
Subject: Re: A question of physics
Date: 8 May 2003 16:58:40
Message: <3ebac500@news.povray.org>
> Reflection is an inherent effect on all interfaces between materials of
> different optical density (i.e. ior, speed of light in the material)

Right. That would seem to explain why no one has ever managed to make
invisible glass for windows yet...

> The amount of reflection depending on the incident angle and the materials
> can be calculated with the fresnel equations.  This works for both a
> transit from less dense to more dense medium as well as the other way
> round.  More information can be found in the links from:
>
>
http://www-public.tu-bs.de:8080/~y0013390/pov/water/water_app1.html#reflect

...and once again I'm left saying I'll check it out later... oh to have more
time! lol

Thanks.
Andrew.


Post a reply to this message

From: Peter Popov
Subject: Re: A question of physics
Date: 9 May 2003 03:14:33
Message: <j8lmbv06alojocq1n85roto7ud1kudf0gt@4ax.com>
On Thu, 8 May 2003 21:54:54 +0100, "Andrew Coppin"
<orp### [at] btinternetcom> wrote:

>...unless it's an even-thickness slab, viewed exactly square-on *grin*

You'll see the edges and side walls due to perspective unless the side
walls are parallel to the viewing rays, but then again you'll have to
look at it with one eye closed.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg


Post a reply to this message

From: Christopher James Huff
Subject: Re: A question of physics
Date: 9 May 2003 11:22:16
Message: <cjameshuff-FE1A25.11221809052003@netplex.aussie.org>
In article <3eb95e52@news.povray.org>,
 "Andrew Coppin" <orp### [at] btinternetcom> wrote:

> Is it possible for a transparent substance to be non-reflective? Or are all
> transparent substances inherantly reflective to a certain degree?

All known substances are reflective to some degree. (Though neutronium 
may be an exception...)

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


Post a reply to this message

From: Christopher James Huff
Subject: Re: A question of physics
Date: 9 May 2003 11:25:42
Message: <cjameshuff-42DB0B.11254409052003@netplex.aussie.org>
In article <3eba0869@news.povray.org>,
 "Andrew Coppin" <orp### [at] btinternetcom> wrote:

> Hmm... gases don't *appear* reflective... but does a gas have a surface???

Mirages. The varying density can cause reflections.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


Post a reply to this message

<<< Previous 6 Messages Goto Latest 10 Messages Next 10 Messages >>>

Copyright 2003-2023 Persistence of Vision Raytracer Pty. Ltd.