Experiment : Double Slit

Hi !

I tried to reproduce the Double-Slit experiment with a cheap red laser-diode (<1mW).

Below are various results obtained from some variations of the experiment ... (with a double slit, with a pinhole, with a thin wire, and with a hair (and also with a single slit who gave almost the same result than with a hair))

I also tried to reproduce it with an other source of light (and got electrocuted). But so far, I'm not satisfied by the results I obtained with the light bulb, and I failed with the sun.

Do you have some experience to share about this experiment ?
Do you have successfully reproduced it with an other source of light than a cheap laser diode ?

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http://www.youtube.com/watch?v=2KD9ICmaiGs#
this is a video of what i think is going on with double slit,first you have to relise that we look at a small cross section of what i think is there,in my video i try to show the bigger picture easer to look at video than explain but in a few words,2 newton rings with the inner edge pinched together, and take a small cross section,lol said isnt easy to explain my video should help
comments welcome
kevinstuartfr0st
chooseausername (author) 10 years ago
They are very boring ........ :-/ I've spent the two last hours to quiz Google ....... I'm unable to find any picture showing the actual results of the experiment with a NON coherent source of light (sun or light-bulb). They will show you results obtained with lasers, with electrons, with "water", they will give you simulations, theories, tons of blabla, equations, drawings and even fake 3D illustrations, but NONE OF THEM seems to actually have reproduced the original Young's experimentation ... So, how could I compare my potentially wrong results with scientifically validated results if no one provided any ??? Well ......... that's not serious ...
...the original Young's experimentation...

Unfortunately, according to Wiki:

Tony Rothman in Everything's Relative and Other Fables from Science and Technology argues that there is no clear evidence that Young actually did the experiment.
chooseausername (author)  Kiteman10 years ago
... I picked-up an experiment in the middle of thousands, and this experiment is probably just a legend. How lucky am I ? ... It's a great disappointment. Thanks Kiteman. I did not read the English version of this article ... In the French one, Tony Rothman is not mentioned. This morning, I've made a hole into the shutter of the window, and tried with a ray of sun : it did not work. I did not even got something close to what I got with the light-bulb ... (sun rays are highly paralyzed compared to light-bulbs rays. It should have worked like with a laser ?) I will study a little bit more the theories behind all of that ...
The english word is polarised (all waves vibrating in the same plane). Paralysed = unable to move (for example, because of a broken back).

Sunlight is not polarised in one plane - it has light vibrating in very plane ("circular polarisation").

Polarising the light might help to get the desired results - either pass the sunlight through a polarising ("Polaroid") lens, or reflect it off a mirror at a low angle. Once you've polarised the light, pass it through a slight that is perpendicular to the plane of polarisation.
Kiteman Kiteman10 years ago
Oops - messed up my formatting:

The english word is polarised (all waves vibrating in the same plane). Paralysed = unable to move (for example, because of a broken back).
chooseausername (author)  Kiteman10 years ago
Oh ! I did not wanted to write "paralyzed", but "parallelized". I did not notice it ...

Yes, I wanted to say "parallelized", like the light of a laser beam =o)
Ah, I see. In that case, the phrase is "much more parallel". Parallelised is not (currently) a real word.
chooseausername (author)  Kiteman10 years ago
Thanks =o)

I will try again tomorrow (if the sun comes to the rendezvous) with a polarized filter (they are old, damaged and low quality, but I don't have better) ...

Also, I was thinking about adding a color filter to reduce the spectrum, but I don't have any of it ... (I will try with a flattened drop of ink between two microscope slide, but I doubt that will do the work ...)

I don't think you need polarized light, but it should definitely be monochromatic to get a clear interference pattern. Try splitting a sunbeam with a prism.

By the way, here is a copy of Young's original paper:

Experiments and Calculations Relative to Physical Optics (page 68-76).

Note that he mentions seeing "fringes of color" - a clear indication he wasn't using monochromatic light. The interference pattern for each frequency is proportional to the wavelength of the light, so if you use light that is not monochromatic, the different interference patterns will overlap each other. So instead of a clear dark-light pattern, you get bands of different colors.
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