Interesting experiment

Since this is the off-topic forum...

Here's an interesting experiment. Get 3 flashlights and tape red, green, blue cellophane to each of them (one each). In other words now you have 3 lights, one with a green beam, one with a blue beam, and one with red beam.

Aim them at a white piece of paper and try to make them all converge at the same spot. The combined light will more or less be white.

Hold your hand up in front of the white piece of paper and now you will see three different shadows since there are three lights. However one shadow will be yellow, one will be cyan and one will be magenta even though the three lights are red, green and blue.

The three colors that you see are the complementary colors for the colors used on the lights.

If you have any colored cellophane give it a try. It's a little more interesting effect than it sounds like (as I describe it).

What's happening is that as your hand blocks part of each of the different beams you see the combination of the effect of the two remaining beams .

Before doing this experiment you can also see the additive effects of color mixing by trying out each green and red focused on the same spot give you a yellow spot for instance.

Well, at least I posted this in the off-topic forum :)

I think you have too have much time on your hands- lol. But if I did some colored cellophane I would try it!

Bored eh? At least you went out somehow creative to kill the boredom. :)

Interesting, It would be nice to see a video.

I seems to remember some experiment at school.

Light tru a prism showing a light spectrum with the colors.

Don´t recall what kind of light we used thou.


Yeah and can you do some Rabbit and Donkey shadows, please.

where in the hell did i put that cellophane ????

On the front of the flashlight, with tape or something improvised I think

That's the interesting thing...sunlight is full spectrum and will show all the colors through the prism but a low spectrum street light for instance would only show some colors.

Not a video but here is a photo showing the effect:


Step away from the bong son to much of that stuff might kill your last flickering brain cell, OK.

I'm never that creative in my spare time! :)

I have a challenge for you then :) don't need colored cellophane! Either go to the grocery store and spend $3 for the mixed pack of food coloring or go to your kitchen if your wife likes to bake and perhaps she has some already!

I saw the food coloring tonight while in the grocery store and bought some just to try this out before suggesting that someone else do it :)

Everyone on this board has 3 flashlights so no issue there :) So just get 3 clear drinking glasses and fill them with water. Put a few drops of green, red, or blue food coloring (one color per glass) in the glasses.

Put a flashlight behind each glass and stand a white piece of paper or cardboard 6 inches or so in front of the glasses. All this can be done on a desktop. Stand up something like an Eneloop a few inches (or less) in front of the white background. The object (Eneloop) is to have something that will create shadows.

Aim all the flashlight/glass combinations at the Eneloop and turn them all on. You will get six different colors. Position the lights for the best effects. You will get the 3 primary colors in the areas where they don't mix, you will get magenta, cyan, and yellow in areas (shadows) where only two colors are mixing.

It seems odd to shine red and green light together and get yellow! Where all three hit one point you get white light as well.

It's quite fun actually!

you have me thinking. What would happen if you put three different colored cellophane discs over each led of a 3 xml light?

It would be interesting (and I'm assuming you mean one color per led). It all depends on how they are focused (I don't have any 3 led lights). I'm assuming that they have some overlap and some non-overlap so you would get the same effect as described above if you shined the beam on a white wall and had some object in front of the wall to cast a shadow.

That's an interesting thought that I hadn't considered. Unfortunately I don't have any 3 XM-L lights.

If someone does you can probably get some red, green, and blue cellophane either in the school supply section of a store or from the wrappers on various hard candy.