What is light? Is it a particle or is it a wave? What an imprudent question! As we know, these are not mutually exclusive characteristics. “Particle” describes the composition of a substance and “wave” describes the motion of it. Right?

But…, wait…, so…, that still doesn’t answer the question… Is light a particle or a wave? Let’s find out!

Today, we're going to add a new piece of equipment to our laboratories and perform a mind boggling experiment with astronomical implications!

First, we will be constructing an Interferometer, a useful piece of experimental optical equipment capable of performing a variety of tasks in a laboratory setting including the Michelson-Morley Experiment, the Sagnac Experiment and others. Specifically though, we will be building a common path Interferometer with an interesting variation. Our version will be taking the approach of physicist Robert Young's 1801 Double-Slit Experiment so our Interferometer will split one single beam of light into two by passing it through two small openings.

Next, we will examine characteristics of moving particles and those of waves moving through a substance. We will then use our new Interferometer to perform the Double-Slit Experiment ourselves. Next, we will observe the result and compare it to what we learned in our previous experiments. You’ll be astounded at what you find!

Let’s begin!

Step 1: What You'll Need

Before we get started on this project, there's a few things we'll need. Unlike the experiments of the 19th and 20th centuries, our project can be made from now easy to find materials and built in a way where the experiment can be accurately replicated anywhere and performed a multitude of times with ease.

Robert Young found that the sun would be the optimal light source for his experiment. And it was, ...at the time. See, for the purposes of what we're going to be doing today, just as in his Double-Slit Experiment, we need parallel bands of light for comparison purposes. The problem is that most light sources emit their light radially, out in all directions, which criss-cross. The sun does too, but since it is a great distance away, the sun's rays are nearly parallel. (Think: a radius of 1cm makes a sharp curve but a radius of 1km looks almost like a straight line.) So, the sun is a fairly good light source, but a laser is better! A laser beam is a highly parallel light source which is what allows it to travel a large distance and still appear as a small dot.


(1) Laser- 630-650nm, <5mw, 4.5v

(1) Project Box

(2) Insulated Wire

(1) 3AA Battery Holder with Switch

(3) AA Batteries (Make your own!>> DIY AA Batteries!)

(1) 32AWG Copper Wire

(1-2) Wire Connectors

(1) Pvc Pipe with Cap

(1) Plastic Ramekin or similar item

Shrink Wrap Tubing


Large Drill Bit

Small Drill Bit

Sanding Bit

Hole Punch Bit

Soldering Iron & Solder



Various Tape, Masking and Aluminum Tape or Electrical Tape

Make due with what you have on hand if need be. I painted a metal cookie box black for the enclosure, a small plastic dish or bottle cap works in place of a ramekin, inexpensive lasers are typically more than sufficient. Feel free to get creative with the rest of the parts as well.

*Read warnings and take cautions when working with lasers.

<p>Check out the <a rel="nofollow">Frequently Asked Questions</a>, then perform the experiments yourselves; it's a lot of fun!</p>
<p>when is your book on sale? </p>
<p>Stay tuned at www.DrewPaulDesigns.com</p>
<p>wow, interesting stuff. Love it! </p>
<p>Only mentioning Einstein's name drove my quackery meter at 50% of quackiness.</p><p> Now, I'd like to learn what exactly this experiment supposedly proves or disproves.</p><p>I know my Physics (to a point of feeling chill with Hermitian operators or eigenproblems), so choose your words carefully. </p><p>Thank you.</p>
Drewpauldesgns: if this were a debate i would say you have won quite handily. Well said. I respect your patience, tolerance and humility. I would love to read some of your publications if i could. (Warramcat46@gmail.com)
<p>One day internet peoplez will stop talking about what they know nothing about... DrewPaul, your experiment is flawed and I am appaulled that this blatant ignorance would end up on this wonderful website. Thank you for participating in the dumbing down of the masses.</p><p>Unless your point was to get people to think about it and disprove you. In which case, nice troll.</p>
There are two side to every coin, friend. Thanks for reading. Give the experiment a try, its a lot of fun!
<p>I did those experiments. With an actually controlled environment, and with proper instruments. Your &quot;double slit experiment&quot; is, as a matter of fact, not that. It's a diffraction experiment. First flaw.<br>I could go on like this, but from reading the comments a great amount of people have already properly made all the points I had to make, and you cannot be swayed from your stubborn and erroneous points of view. I'm sorry for you, and I sincerely hope you don't convince people of this fallacy.</p>
Let me, by the way, remind you (or point out if this is the first time you've considered it) that the &quot;definitions&quot; of terms you keep referring to are simply mankinds attempt to promote unified understanding, and may or may not be accurate in and of themselves. Our &quot;definition&quot; of a wave or a particle, for example, may be completely incorrect.<br><br>Next, remember also that science is mankind's best attempt at explaining the natural universe. I can guarantee that everything we call scientific proof or law is, in some way shape or form incorrect. Why? Well, for one, how do we attempt to explain science? Through equations. These are equations that &quot;best fit&quot; the natural phenomenon. The equations are not THE phenomenon itself, and therefore has its flaws. (Remember where math came from, also an invention of mankind, not the universe, math was &quot;invented&quot; to help us understand and manipulate for our improvement the world around us)<br><br>In other words, you cannot result to definitions from wikipedia to prove anything scientific.
By the way, you should do a little research on the Huygens-Fresnel principle of optics and the interference patterns of light passing through an aperture at varying distances from the aperture.<br><br>Your spray paint example is completely flawed when trying to compare its effects to that of light. The intensity patterns you see with the interferometer with light is located in what's known as the Fresnel and Fraugnhoufer regions. These cases are when the viewing location is a specified distance (decently large) from the aperture. When near the aperture, you most definitely see the same image as what you saw with your spray paint. I suggest you put your interferometer much closer to the wall as this is most definitely replicable. :)<br><br>Cheers!
<p>The question of the Merli-Missiroli-Pozzi and Feynman two-slit <br>electron Experiment experiments where it is purported that &ldquo;electrons&rdquo; can pass <br>through a double slit and result in an interference pattern has been brought up <br>several times. If we are to base our entire scientific view on a few iterations <br>of a single experiment, then we should examine that experiment closely and hold <br>it to a higher standard. <br> <br>By reviewing their experiments and examining the instruments with which they <br>were performed, you will find that in any case that yields the ostensible result; <br>the charged &ldquo;electrons&rdquo; are being propelled by way of an electromagnetic field. <br>Firstly, it is this charge that moves the electrons and therefore propels them <br>only along the wavelength of this electromagnetic wave. Additionally, it is also <br>essential to note how the &ldquo;electron&rdquo; pattern data is collected, by <br>electromagnetic means. Consequently, this experiment cannot therefore be <br>replicated in such a way that isolates the particles and is therefore invalid. <br> <br>In order to validate this experiment, it can be performed as follows: Perform <br>the test in a similar experimental environment but with the following <br>adjustments. In order to propel the &ldquo;electrons&rdquo; in a way which isolates them <br>from any outside electromagnetic wave, propel the electrons by way of a linear <br>mechanic force of your choosing. This will validate the non-isolation errors of <br>these previous experiments. Next, in the interpretation of the data <br>non-isolation errors can occur as well, therefore retrieval of data should be <br>isolated to non-electromagnetic means, preferably mechanical, as well. By <br>performing the experiment with these errors resolved, it is then only the <br>particulate electrons that are being isolated in the experiment and output <br>data.<br> <br>In any and every occurrence wherein these non-isolation errors have been resolved, <br>no interference pattern can be detected.</p>
btw why did you put electrons in inverted commas? Do you not believe in electrons either?
<p>Good question! The term photon to describe a particle with the exclusive ability to carry light, the term electron to describe a particle with the exclusive ability to carry electricity are as equally as inaccurate as the invention of, say, a &ldquo;soundtron,&rdquo; a particle which has the exclusive ability to carry sound.</p>
<p>I'm a chemist. An electron for me is one of the 3 components of an atom. It is definitely not &quot;a particle with the exclusive ability to carry electricity&quot; and should never be thought of as such.</p>
<p>I agree with you there.<br><br>Have a great day, my friend.</p>
also you talk about holding experiments to a higher standard. But your spray paint experiment is abysmally designed.
<p>Don't be silly. This test was designed to replicate one from a laboratory setting for the Instructables community. It was designed to be easy to perform with easy to access materials. Also, it is in fact only a method for developing a hypothesis, not the experiment itself.<br>For a scientist like yourself, check out the FAQ section for instructions on how to perform the test in a way with far lower tolerances and let us know what you find.</p>
<p>I agree it is easy to perform. But unfortunately the conclusions and hypothesis you draw from it are incorrect due to the flaws in the design of the experiment. 'Particles' can and do behave like 'waves' and vice versa due to wave particle duality. </p>
<p>I concede that wave-particle duality is still controversial among a minority of physicists. But even as they propose alternative explanations they themselves still accept that 'particles' have been observed to behave like waves in some instances and their alternative theories attempt to explain this behaviour. Your statement that it is impossible for particles is false.</p>
Wrong again I'm afraid. this experiment has been performed with neutral particles, not just electrons.
<p>To which experiment are you refferring?</p>
<p>I am referring to the double slit experiment. http://www.livescience.com/19268-quantum-double-slit-experiment-largest-molecules.html</p>
<p>Here's another article that raises some questions. If, as Einstein so boldly proclaimed in his &quot;On the Electrodynamics of Moving Bodies,&rdquo; &quot;light is always propagated in empty space with a definite velocity c(186,000 miles per sec), how are these scientists able to slow light in a vaccuum?...</p><p><a href="http://rt.com/news/225879-light-speed-slow-photons/" rel="nofollow">http://rt.com/news/225879-light-speed-slow-photons...</a></p><p><a href="http://news.harvard.edu/gazette/1999/02.18/light.html" rel="nofollow">http://news.harvard.edu/gazette/1999/02.18/light.h...</a></p><p>Wrong again, Al.</p>
erm the experiments in those links are based on the particle nature of light. It's almost as if Einstein being slightly wrong about some things doesnt make you right.
<p>Indeed, they may have been performed under the assumption of the particle nature of light, however, all things considered and by extension, this definitively disproves the postulate made in &quot;On the Electrodynamics of Light.&quot; I think we can agree on that.<br>This is science, my friend, there is no slightly wrong, especially with something of this magnitude.</p><p><br>It's been fun chatting with you, btw.</p>
<p>As a matter of fact, there IS &quot;slightly wrong&quot;. Newton said that F = d(mv)/dt was he wrong? <strong>NOPE</strong>. Not for that time. Not for today. When you design a car you can bloody well use his equations as a car going at 90 mph isn't nearly as close to C for you to consider the relativistics effects. It would be a waste of time to calculate all the aerodynamics and strains of a car with Einsteins physics when the difference from his to Newtons physics would be less than 0.001%. The imprecision of the manufacturing is probably bigger than this.</p><p>Nobody ever said that Einstein is 100% right and that the study of physics is 100% sealed and nothing new is out there to be discovered. But the way you discredit their work with empty critiques is absolutely outrageous!!</p><p>I'm a chemical engineering graduate, far from being a physicist, but from what I learnt from uni might do you some good, presuming that you leave your arrogance to the side and stop being lazy and read some actual science for once. OMG.</p>
<p>Thanks for checking out my Instructable! Didn't mean to upset you. </p><p>While I thought it would be fun to package my some of my findings in this fun article, make no mistake, this is partly the result of more than 10,000 hours of research and several hundred original and replicated experiments.<br><br>Check out the FAQs and try the experiment for yourself; its a lot of fun!</p>
so we can only believe experiments we perform ourseĺves (which is what you keep saying) unless they back up something you've decided you want to believe like those in the links? OK, I think your &quot;objectivity&quot; has become very clear.
<p>Based on the definitions of &quot;particle&quot; and &quot;wave&quot; light cannot be both. A particle is matter and a wave is a specific motion of matter. Light is therefore only the vibration of the medium through which it passes.<br>Don't take Wikipedia's word for it. try the experiment for yourself and let us know what you find.</p><p>&quot;People's beliefs and convictions are in almost every <br> case gotten at second-hand, and without examination, from authorities who have <br> not themselves examined the questions at issue but have taken them at second-hand <br> from other non-examiners, whose opinions about them were not worth a brass farthing.&quot;<br> <br> - <em>Mark Twain</em></p>
<p>&quot;Based on the definitions of &quot;particle&quot; and &quot;wave&quot; light cannot be both.&quot; You are absolutely right about this. It's not both. It is <em>neither</em>. Light is a quantum, extremely well described (to an accuracy of roughly 1 part in 10^15) by quantum electrodynamics. </p><p>Quanta present wavelike (but NOT &quot;just wave&quot;) interactions, such as constructive and destructive interference, diffraction, and apparently non-local behaviour. Quanta also present particlelike (but NOT &quot;just particle&quot;) interactions, such as discrete, point-like behaviour, specific energy and momenta per discrete unit, and localized detection.</p><p>If you really think you have a better model for how electromagnetism works, you're going to not only make calculations of observed behaviour which is at least as accurate as QED, you are also going to have to be able to make _predictions_ of observable behaviour (to the same precision) which are different from the predictions of QED. Otherwise, you're just blowing smoke.</p>
<p>It's not a new model so fortunately I need to do no such thing. The experimental data of Michael Faraday and Nikola Tesla and the mathematics of James Clerk Maxwell pretty much covers all the bases. Look them up.</p>
<p>Okay, so you're just a quantum denialist. As I noted before, it's ironic that your project makes explicit use of science which you insist doesn't exist.</p>
<p>So true. I honestly can't decide if this is a massive wind-up or someone stubbornly refusing to move on from 19th century physics. I mean can you imagine what a fuss something like quantum entanglement would cause here?</p>
<p>Denial. It's not just a river in Egypt. And denialism is often the refuge of those who suffer from Dunning-Kruger syndrome.</p>
<p>In an attempt to refrain from a conjecturing argument, I will not make an attempt to assume that if your argument is fallacious, then your conclusion is false. But, you're not giving me much else to work with... </p>
<p>Since you explicitly reject any experimental physics dating from after 1900, it's very hard to have an actual scientific discussion. You make blanket assertions which are not only unsupported by data, they are entirely disproved by data. You claim expertise in an area where your own statements demonstrate either ignorance (lack of training) or willful denial (rejection of information).</p>
<p>I do not, would not and will never reject any experimental evidence that is both replicable and free from error. However, as of this point in time, no such data has been presented to me. <br>To speak of the claims you make would be to participate in your ad hominem argument, yet I will indulge you while sparing the details by saying that my scientific accomplishments are more than noteworthy and have only been possible by application of unwavering objectivity. Furthermore, I make no claims of expertise, a fallacious method in itself, I rely only on data to make assersions.<br></p>
That all sonds nice but isn't true is it? numerous groups have obtained interference patterns from electrons, atoms and molecules. You have repeatedly refuted this. Your spray paint experiment is so flawed as to be pointless. This has been pointed out to you and you have refuted it. You insist only experiments you perform yourself can be trusted yet you have linked to other people's findings when it suits you. Are you surprised people are disagreeing with you strongly? You are insisting your crude spray paint experiment contradicts thousands of other scientist's work and nearly a century of accepted science. The arrogance, that you are right and the rest of the scientific community is wrong, is quite frankly outstanding.
<p>I apologize if I haven't yet addressed you on this point, though I have addressed it multiple times to others. <br><br>Firstly, It is easy to see how confusion can occur on micro and nano levels, <br> <br>however. That is why is is so important, crucial in fact, to observe and <br> <br>examine the natural world around us. Mathematics can be written to any <br> <br>end, experiments outside our realm of sensory perception are riddled with <br> <br>potential areas for error. We must look at the stars in the sky, our <br> <br>oceans and perform simplistic experiments with no room for error or <br> <br>misinterpretation such as this.<br><br>Next, of similar instruments and experiments that I've investigated, Pozzi Feynman, etc., I find a similar phenomenon <br>that results in skewed interpretations of their results. In most cases devices <br>such as these do in fact produce a wave, either, rather than or along side the <br>propagation of particles. These are biased experiments performed with the explicit prerogative of avoiding contradiction to the &quot;great&quot; Albert Einstein.<br><br>Thoroughly and objectively investigate each individual instrument diagram and each individual experiment's methodology yourself and you will come to the same conclusion. </p>
ok i give up. Let's put it this way: the skewed interpretations and flaws you see in other people's work is how I view your experiments. We will never agree (although i have the luxury of 100 years of scientific data and the vast majority of the scientific community on my side, you have a couple of crude garage experiments). if you believe you are correct you have a moral obligation to publish it in a journal of repute.
<p>The difference is you can replicate my experiment! That's why it's on Instructables. Try it out; it's a lot of fun!</p>
<p>You can also replicate the interference pattern obtained from electrons (I've seen it done at university). You seem to dislike experiments done with intricate scientific equipment (for some unknown reason you keep talking about looking at the stars, sky and oceans when your experiment is carried out with a man made laser). This is odd. Would you want surgeons to develop new surgery with a kitchen knife and a pair of paper scissors? Your spray paint experiment is flawed as you have not controlled the variables (or even thought about them). How did you choose the slit size? Why did you choose it? What angle does the spray paint come out the can at? Is it just one angle or a number of angles? Does this matter? What's the particle size of the spray paint? Is it uniform? How fast do they travel? Does it matter? How far back should the screen be to view the particles that have passed through? Does it matter? How accurate is it (I can see quite a bit of splatter from the paint in your experiments. Is that diffraction or just splatter? Do you know?). The more unknown variables you have in your experiment, the less likely it is that you can draw any meaningful conclusions from it.</p>
<p>It was a pleasure chatting with you guys!</p><p>I will be publishing some formal materials shortly and our discussion here has helped immensely.</p>
<p>Then let's start with the basics. Please derive the well-known, and extremely well-tested, black body spectrum for radiation, _without_ assuming quantization.</p>
Couldn't agree more
<p>Again with the definitions, defining light as quanta is incomplete to say the least. &quot;Quantum&quot;, plural &quot;quanta,&quot; is defined as the following: &quot;a particular amount&quot;. And, with reference to Physics: &quot;the smallest quantity of <em>radiant energy</em>, the fundamental unit of a physical magnitude.&quot; </p><p>When asked what kind of car you drive, you wouldn't answer, &quot;2400 lbs,&quot; I hope.</p>
<p>&quot;In <a href="https://en.wikipedia.org/wiki/Physics" rel="nofollow">physics</a>, a <strong>quantum</strong> (plural: <strong>quanta</strong>) is the minimum amount of any physical entity involved in an interaction.&quot; (http://en.wikipedia.org/wiki/Quantum). </p>
<p> Again with the definitions, defining <br>light as quanta is incomplete to say the least. &quot;Quantum&quot;, plural <br>&quot;quanta,&quot; is defined as the following: &quot;a particular amount&quot;. And, with <br>reference to Physics: &quot;the smallest quantity of <em>radiant energy</em>, the fundamental unit of a physical magnitude.&quot; </p><p>When asked what kind of car you drive, you wouldn't answer, &quot;2400 lbs,&quot; I hope.</p>

About This Instructable



Bio: I am a tech maniac; from media, marketing and design to alternative energy and more. Check out my website for links to all my projects.
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