Duplicate image from light

[Masha Rosela]

I'm not entirely sure this fits under science education, however it is somewhat science related, specifically light science, and I do need to be educated.

Imagine you are outside on a perfectly sunny day with a nice white piece of tagboard (because it's heavier and harder to blow away) and you hold up, for sake of example, a translucent red piece of glass between the light source, in this case the sun, and the tagboard and the sun shines through the piece of glass and creates a duplicate image onto that tagboard, the shape of which alters depending on what angle you hold the glass.

What is that duplicate image called, please?  I thought it was refraction, but now I think it is something different and trying to dig around on the internet I am having a hard time finding what describes what I am talking about.  I am a photographer who takes pictures of gemstones, my favorite things to play with in photography are lighting and angles and gemstones make the perfect subject for that.  I have two different methods of taking pictures of gemstones with light sources.  The first is as I described with the red glass above.  The second is taking the gem into a dark space and lighting it up with a pen light to create almost an Aurora Borealis type effect, kind of like that scene in Balto with the broken glass.  The second method I realize probably is refractions, it's the "light reflection"/duplicate image I wish to know the title to. 

Attached are some examples.  The first two images are method one that I used in the example with the duplicate image, the third picture is the second method with the pen light.  Actually, that one is from my first time doing a shoot like that where I made a black paper cone with a small hole at the tip and taped it over the flash light of my sister's smart phone.  Yay, resourcefulness!

[Strange]

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Moderator Note

Moved to Physics - seems more appropriate

 

I can’t quite see what is going on (on my phone) but I would say that the overall effect is due to refraction: the bending, splitting and focusing of light as it passes through the material 

The bright lines are probably caustics:  https://en.m.wikipedia.org/wiki/Caustic_(optics)

[swansont]

You have both a shadow and a bright image. Refraction is in play as you (as Strange) have noted. (For the shadow, it's also reflection keeping light away) That bends the light and is also responsible for multiple colors you might see, as with a prism, since refraction is wavelength-dependent

If the material were spherical, even in part, you could form an image of the light source — fires have started because sunlight passed through a glass/crystal sphere and focused the light onto something flammable. 

[Masha Rosela]

8 hours ago, Strange said:

!

Moderator Note

Moved to Physics - seems more appropriate

 

I can’t quite see what is going on (on my phone) but I would say that the overall effect is due to refraction: the bending, splitting and focusing of light as it passes through the material 

The bright lines are probably caustics:  https://en.m.wikipedia.org/wiki/Caustic_(optics)

Thanks!  I wasn't sure!  And yes, I thought refraction initially, but even though I already had an idea on what it meant, last night I got an intense urge to look it up and double check and everything I found pointed more to the second method I use of just allowing light to pass through in any which way the beams go rather than condensing to form a duplicate image.  But honestly I don't really see why that can't be a form of refraction, too.  Thank you!

4 hours ago, swansont said:

You have both a shadow and a bright image. Refraction is in play as you (as Strange) have noted. (For the shadow, it's also reflection keeping light away) That bends the light and is also responsible for multiple colors you might see, as with a prism, since refraction is wavelength-dependent

If the material were spherical, even in part, you could form an image of the light source — fires have started because sunlight passed through a glass/crystal sphere and focused the light onto something flammable. 

So, then both methods I am talking about and showed examples of are refraction, including the duplicate image, yes?

And of course, everyone knows the crystal ball thing.  Many sellers who have crystal balls with exceptional clarity sell with a note to not leave out in light unattended or to cover it when you're not around so a fire doesn't start and there are stories of smooth crystal doorknobs causing fires for the same reasons.  Honestly, if you're going to get a glass or crystal doorknob, get one that is highly faceted or only put it in parts of the house where sunlight will not reach.  Some people.

Thanks, guys, I just wanna make sure I'm using the right word.  I hate it when someone uses a word wrong and you try to correct them on it and explain the right use, but they've been using it wrong for so long that they're set in their ways and insist that they're right and I'm just always worried about becoming that person myself.  So any time I have to use a technical term especially, I always triple check that I'm using it right.