Three glasses - a curiosity

[TonyW]

This is a five minute recreation of an image that I saw recently, complete plagiarism except that I did take the photograph myself. I know it is technicality bad in several respects but it shows one interesting thing to me.

The glass in front (nearest the camera) has plain water in it, the ones behind have food colouring in the water. It is entirely back-lit by already diffuse natural light passing through frosted glass. What surprised me at first when I saw the image was that the colours are reversed in the front glass. It's a good exercise in optics to work out why that is so.

This is somewhat reminiscent of a picture that Mike Buckley showed recently with an array of several rows of wine bottles, but in his case it was all monochrome so that the reversal of colours was not apparent: Wine: Clear Bottles

[george013]

This is a five minute recreation of an image that I saw recently, complete plagiarism except that I did take the photograph myself. I know it is technicality bad in several respects but it shows one interesting thing to me.

The glass in front (nearest the camera) has plain water in it, the ones behind have food colouring in the water. It is entirely back-lit by already diffuse natural light passing through frosted glass. What surprised me at first when I saw the image was that the colours are reversed in the front glass. It's a good exercise in optics to work out why that is so.

This is somewhat reminiscent of a picture that Mike Buckley showed recently with an array of several rows of wine bottles, but in his case it was all monochrome so that the reversal of colours was not apparent: Wine: Clear Bottles

I will remember this one! Wonderful. Now theexplanation.

George

[IzzieK]

Now you made me wonder how we really see colour (or not...)

[Wavelength]

I really like the pattern. How the middle glass acts as a pair of concave mirrors reflecting the colors opposite is really interesting; it inspires me more to experiment. Thank you

[Shadowman]

Nice, thanks for providing visual.

[scully]

All about refraction. The curve of the glass in front means that light from the right rear glass is bent through the curve on the left of the front glass and vice versa. That is if my memory of my old physics classes is correct.

[rachel]

This is great! I'm a physics teacher - scully is definitely right about the refraction - although there's probably some reflection going on as well - but I would need time to think about what is really happening here (visualising what is happening to the light rays is a tough one for me because I've always found it hard to imagine things in 3D).

But what a brilliant thing to set up to introduce refraction to a class. Consider it added to my repertoire....

PS - would it work with tumbler style glasses do you think? Or bottles? Or is there something specific about the shape of the wine glass? Off to play....

[george013]

This is great! I'm a physics teacher - scully is definitely right about the refraction - although there's probably some reflection going on as well - but I would need time to think about what is really happening here (visualising what is happening to the light rays is a tough one for me because I've always found it hard to imagine things in 3D).

But what a brilliant thing to set up to introduce refraction to a class. Consider it added to my repertoire....

PS - would it work with tumbler style glasses do you think? Or bottles? Or is there something specific about the shape of the wine glass? Off to play....

I found this one. The second picture is showing a same effect. Tony referred to the winebottles of Mike.

It still doesn't show me the light rays.
If somebody wants to ecxlain it.


George

[Mike Buckley]

Now that I've read the thread, I still have a question: Why are the blue tones being reflected in the base of the glass on the left but the orange tones aren't being reflected in the base of the glass on the right?

I've never gotten around to buying a macro lens, but I'm inspired to get one when I see things such as the blue and orange shapes in the top of the stem of the middle glass. Just gorgeous!

[rachel]

George - I'm going to ask some physicists with better shape and space awareness than I to draw a ray diagram as seen from above. I just can't imagine it well enough myself.

[george013]

George - I'm going to ask some physicists with better shape and space awareness than I to draw a ray diagram as seen from above. I just can't imagine it well enough myself.

I don't think it's a matter of refraction, but reflection. Light passing the glass being refracted goes further in a parallel way. It goes in the glass and out the glass, the material I mean. But due to the form of the glass, the subject now, the critical angle is passed and the light is reflected. But where does that happen? Just a guess.

George

[TonyW]

Thanks for the comments. I think Rachel is right in saying that to understand it you need to draw the rays and pay attention to the way they are refracted as they pass into the front glass and emerge from it. I used to think that there was some total internal reflection going on but I doubt that now. It's too late at night for me to get into details.

Mike's question about the blue reflection has an embarrassing answer. I spilled some blue water onto the base of the glass and didn't wipe it off properly.

I don't think the shape of the glass is critical. I should work the same way with pure cylinders. Glass and water have slightly different refractive indexes (1.6 versus 1.4 if I remember correctly) but because the glass is thin you only need to think of it as being water.

[george013]

Thanks for the comments. I think Rachel is right in saying that to understand it you need to draw the rays and pay attention to the way they are refracted as they pass into the front glass and emerge from it. I used to think that there was some total internal reflection going on but I doubt that now. It's too late at night for me to get into details.

Mike's question about the blue reflection has an embarrassing answer. I spilled some blue water onto the base of the glass and didn't wipe it off properly.

I don't think the shape of the glass is critical. I should work the same way with pure cylinders. Glass and water have slightly different refractive indexes (1.6 versus 1.4 if I remember correctly) but because the glass is thin you only need to think of it as being water.

I did forget it's filled with water.

George

[Wavelength]

If you quickly scroll up or scroll down, George's tricolor posting, you will see violet circle getting pink color along its upper or lower edge...how that comes?

[Wavelength]

I humbly feel it is a case of concave mirror formation on the inner surface, reflecting the color on the opposite side....
(suffering total internal reflection)

[george013]

I have something else. All refraction.



It's a sketch. Don't look at the used angles. But I think the refraction is in the right direction.

George

[bnnrcn]

Thanks for sharing Tony , a nice image and lesson

[scully]

This is great! I'm a physics teacher - scully is definitely right about the refraction - although there's probably some reflection going on as well - but I would need time to think about what is really happening here (visualising what is happening to the light rays is a tough one for me because I've always found it hard to imagine things in 3D).

But what a brilliant thing to set up to introduce refraction to a class. Consider it added to my repertoire....

PS - would it work with tumbler style glasses do you think? Or bottles? Or is there something specific about the shape of the wine glass? Off to play....

Rachel,

The resultant images in cylindrical prisms would be reversed and spherical ones would be upside down as well as reversed, right? Bottles (clear glass) and tumblers would work better because the lens would be simple rather than compound, I think.

What you are seeing here is almost all refraction, the light rays from the glasses behind passing through the lens created by the glass and water in front but being bent by the lens thus giving the impression that the light came from another place, ie the red and white appearing on the opposite side to what your brain thinks that they should. The amount that the light bends depends on the difference in the refractive indices of the two mediums, water and air (technically three as glass in involved) and, I think, the tightness of the curved surface of the glass

Reflected light does not pass through but bounces back. Anyway, my two cents worth:-)

Steve

[Wavelength]

Light entering the glass suffers refraction, ie, bent; then it traverses the new medium water, then all those rays that meet the glass on the other side at 45degree suffers total internal reflection, since here light moves out from denser to rarer medium(glass to air; not water to glass) and comes back, which is seen as the reflection to our eys.... i suppose

[george013]

That's what I draw. The refracted light ray.

George