# Wood/Glass/Metal Help making one way glass

Hello, i'm wondering if you can inform me about that kind of light which be projected on a glass and it helps us to see it's reflection only for the viewer and not for anyone the other side .
all proposals and methods are welcome.
even if it is necessary for the light to pass on a chemical substance.
thank you cordially
Mehdi from the National School of Marine Sciences in Algeria

#### Attachments

• 61.5 KB Views: 136

#### phinds

Gold Member
It's not up to the light, it's up to the glass. One-way glass has been around for decades.

It's not up to the light, it's up to the glass. One-way glass has been around for decades.
thanks for your answer, but i am looking for a solution for the light.
and One-way glass you can not see the other side

#### phinds

Gold Member
thanks for your answer, but i am looking for a solution for the light.
and One-way glass you can not see the other side
??? One-way glass does exactly what your picture shows.

#### DaveC426913

Gold Member
??? One-way glass does exactly what your picture shows.
Weeeelllll, it does exactly the opposite of what his diagram shows.

With one-way glass, the person in darkness can see the person in the lit room. Whereas the person in the lit room can't see the person in darkness.

#### DaveC426913

Gold Member
Hello, i'm wondering if you can inform me about that kind of light which be projected on a glass and it helps us to see it's reflection only for the viewer and not for anyone the other side .
Madou, if you move the light to the opposite side of the glass, without changing anything else, you have your solution.

Last edited:

#### phinds

Gold Member
Weeeelllll, it does exactly the opposite of what his diagram shows.
Good catch, Dave. I was ignoring where the light is because I knew the solution couldn't be with the light.

Madou, if you move the light to the opposite side of the glass, without changing anything else, you have your solution.
thank you for your answer, the final result that I want to get it is like a stained glass just in projecton a light.
if you see what I want!
like this ! but only with light

#### Attachments

• 43.4 KB Views: 121

#### phinds

Gold Member
thank you for your answer, the final result that I want to get it is like a stained glass just in projecton a light.
if you see what I want!
like this ! but only with light
This is just tinted glass (not what "stained glass" normally means, but not too different), and the view from the inside is partially obstructed by the glass. Again, the solution is with the glass, not with the light.

#### DaveC426913

Gold Member
Diagram added in post 6, for clarity.

Homework Helper
Gold Member
Window tinting?

#### phinds

Gold Member
Yes , but only on projecting light
I have no idea what you are talking about. Tinted windows are tinted regardless of light, unless you are talking about the kind of light that is used in glasses (spectacles) so that they slowly turn dark when you go out in the sunlight. In either case, the solution is in the glass, not the light and the visibility is the same from both sides

#### sophiecentaur

Gold Member
Glass of any kind is no truly ‘one way’. It will let the same fraction through from either direction. Ant one way system relies on the Observer side being dimmer than the place he is looking at. The performance is always better if the Observed Side of the glass has stripes of mirror. This increases the contrast between the bright shiny strips and the dark gaps as seen from the Observed side.

#### phinds

Gold Member
Glass of any kind is no truly ‘one way’. It will let the same fraction through from either direction. Ant one way system relies on the Observer side being dimmer than the place he is looking at. The performance is always better if the Observed Side of the glass has stripes of mirror. This increases the contrast between the bright shiny strips and the dark gaps as seen from the Observed side.
Actually, it's not normally done in strips. Here's from wiki:
A one-way mirror has a reflective coating applied in a very thin, sparse layer -- so thin that it's called a half-silvered surface. ... The room in which the glass looks like a mirror is kept very brightly lit, so that there is plenty of light to reflect back from the mirror's surface

#### sophiecentaur

Gold Member
Actually, it's not normally done in strips. Here's from wiki:
The simplest example (that was used in shops and offices) used quite wide silvered strips which I suspect was a modified regular mirror. The lowest tech you could imagine and it did the job.
Other technologies (better) are available for Physicists.

#### phinds

Gold Member
The simplest example (that was used in shops and offices) used quite wide silvered strips which I suspect was a modified regular mirror. The lowest tech you could imagine and it did the job.
Interesting. I've never seen one of those. A couple of the stores I worked in parttime when I was young had the kind wiki talks about and of course all the cop shows have that kind as well.

#### sophiecentaur

Gold Member
Interesting. I've never seen one of those. A couple of the stores I worked in parttime when I was young had the kind wiki talks about and of course all the cop shows have that kind as well.
The strips(iirc) perhaps had a pitch of 15cm. Not too coarse to spot and recognize a customer coming into the shop and, of course, the local glazier could make up a replacement to any size.

EDIT: that's 15mm and not 15cm. Durrr!

Last edited:

#### sysprog

Hmm -- what kind of light . . . oh, yes, one or more of the impossible kinds . . .

Merci, Monsieur Magritte.

#### phinds

Gold Member
Hmm -- what kind of light . . . oh, yes, one or more of the impossible kinds . . .
??? What on Earth does that image have to do with this thread?

#### sophiecentaur

Gold Member
??? What on Earth does that image have to do with this thread?
As with many, the thread has a mind of its own. The agenda was never really declared.

#### phinds

Gold Member
As with many, the thread has a mind of its own. The agenda was never really declared.
Well, c'est la vie

#### sysprog

??? What on Earth does that image have to do with this thread?
What does the "kind of light" have to do with the transparencies and reflectivities of a window pane? The image was by me intended as a reductio ad absurdum in support of the position already expressed by you; it's a fantasy image in which light behaves inconsistently in a manner depending on viewer attention viewpoint. How can it be daytime in the sky while it's night-time on the ground in what is otherwise approximately the same location?

#### anorlunda

Mentor
Gold Member
Please, let's try to focus on helping the OP.

"Help making one way glass"

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving