Author Options:

Instructable for building a proper light-tight box? Answered

I tried searching for "dark box," "light box," "film box," "film processing," even for pinhole cameras. I couldn't find an I'ble which directly teaches how to make a high-quality light-tight box (felt lined, gasketed locking lid, etc.). Did I just choose poor keywords? Do any of the photo-gurus here know whether such an I'ble exists? For a couple of single-photon Physics I'bles I'm working on, I've realized that asking people to seal up a whole room and make it totally light-tight is ridiculous and impractical. I ought to get the same effect with a dark-box using a good viewport and head shroud. Rather than writing a whole I'ble myself, I'd rather cross-reference something which already exists.


What is the min / max dimension you require?

I was envisioning something maybe half a meter on a side. That gives enough projection distance to get naked-eye visible interference fringes, but not so big as to be unweildy. I'm not in a position to make and document such a thing myself, so I was hoping someone might already have an I'ble for it that I could just reference.

Maybe a long shot, but I was thinking about PVC tubing (larger sizes).
It is easy to cut, it is rigid to attach stuff, there are many blind caps and T-pieces and there are x-overs available to build whatever you like...

Without the box, I just discovered that two razor blade slits in paper about 3.8in apart will give a very nice interference pattern from my video projector on a wall about 8 feet away.

Really? That's impressive. You put the slits about 10-15 cm away from the projector lens? I knew those bulbs were bright, but I didn't realize they put that much light out. A setup like that would be awesome for a classroom demonstration of interference and diffraction.

Sorry, I meant 3/8in., not over 3in.

I also discovered you can get the effect with two fingers. I think the light is spreading out from the different sides of the gap between the fingers and causing the interference pattern.

If there's only a single slit, it's a diffraction pattern. Visually, the two look quite similar, but they're quantitatively different (and you can extract different information from the patterns).

Thanks for the clarification on dimensions. For my projects (see my profile) I think you still need a light-tight box, because the intensity is designed to be extremely low (single photons). Nevertheless, this is a great demonstration.

. How about a cardboard box, head-size hole cut in the bottom of one end, "drape" around head hole?

That's what I'm starting to imagine. My concern is how to mount the laser pointer (and eventually the double-slit grating and camera) and keep everything nicely aligned.

. It may need to be large/long enough that it will have to be set on a table, with the access hole hanging over the edge. Or view from the end, a la old glass-plate cameras. Someone in one of the sewing groups should be able to design the "drape" for you.
. Mounting it to a table will help with stability. Or piece of plywood for the bottom.
. Cardboard can usually be obtained free, so size shouldn't add to the expense. If one has enough space, one could build a cardboard box big enough to crawl inside of. Seal the entry with opaque tape from the inside. Remember to come out for air. ;)

Shipping container?

Mmmm...you mean one of those plastic or aluminum cases? That's a great idea.

i was thinking the big freight containers (room size), but If you don't need a full size labs those might be a better idea.

Ah, I see! I really want this to be something a person can do for themselves, at home. One of the things about both of these experiments which appeals to me is that QM doesn't have to be something "physicists" do in "labs," but it something that anyone can get a hold of.

Well...how about a cardboard box lined with dark fabric or black construction paper? Or wood? Or something.

Yup, a "light-tight box". The standard method is to line it with black felt. The hard parts here are
  • a viewport to look in without compromising the light-tightness
  • attaching a camera (for the double-slit experiment)
  • keeping the laser and other stuff aligned in something you pick up and move
Hmmm. Okay. I have a couple ideas:

  • A binocular without lenses inserted into a custom cut hole in the box. Edges sealed with that window insulation putty stuff. And maybe heavy black cloth to go over head while using.
  • Duct tape!
  • Seriously. How about just putting it on the end of a rod, or square shaped stick (like a broomstick, or preferably thicker) and just attaching that to the bottom of the box?

Hah! Yes, it does, and it's one of the pages I had found and bookmarked once I struck out on I'bles :-) Thanks!

You know, I don't think there is one - digital photography has reduced the need.

By the way, thanks for the follow up! I've been coming to the same conclusion.