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!
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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
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.
Step 2: Prepare Your Battery Pack
Heat your soldering iron and strip the ends of the Battery Holder leads and Insulated Wire. Slip on some shrink wrap and extend the leads by soldering on a length of wire to each. Before you're finished, insert your batteries and lightly tin the ends of the wires to prepare for the next connection.
If you don't have any AA Batteries, MAKE YOUR OWN!
See how by checking out my last Instructable: DIY AA Batteries!
Step 3: Wire Your Laser
To wire your laser we will need to make a quick modification. In order to take data while experimenting, we'll need to leave the laser on for extended periods of time. This means we'll need to replace the button with a switch and replace the batteries with some of a higher capacity. The Battery Holder we just prepared will serve both these purposes. We'll just need to connect it.
To access the leads we'll first remove the Laser's battery cap and remove the batteries. Next, grind down one side of the Laser's case, as shown, or cut it away however you see fit.
According to the original battery orientation and the diagram, the spring is the negative ground and the case will serve as the positive lead for the laser. With your soldering iron attach one wire to the spring and use a piece of shrink wrap to secure and cover the spring to avoid shorts. Then, drill a small hole in the case, wrap your positive wire around securely, solder in place and shrink wrap that connection as well. Connect the ends of each wire to your Wire Connector(s).
Your laser module is now complete and ready to be temporarily wired up to test your connections. Once tested, continue to the next step.
Step 4: Assemble a Double-Slit
We will be replicating Robert Young's Double-Slit Experiment and will need an appropriate setup. To do so, we'll attach our tape to create a rectangular slit with a wire placed precisely in the center to create two parallel uniform evenly spaced slits.
First, wrap the Laser module with tape to firmly hold down the Laser's on button and so that it fits snugly in the piece of PVC Pipe.
Then, hold a straight piece of wire directly over the Laser's lens, as shown, and tack in place with glue. Make sure the wire is centered, straight and taut. See photos.
Next, cut two pieces of tape to go on either side of the wire. Electrical tape will work but aluminum tape results in a crisp, straight edge and yields the best results. Lay each piece parallel to and on either side of the wire, like the photo. You will want to leave a gap equal to the width of the wire for uniformity.
Once the slits are of the correct width, straight and parallel, you can wrap the Laser's tip with tape to secure everything in place.
Carefully connect power, turn on the switch and aim the laser at a smooth surface to test. Some adjustment may be necessary. You will be able to see a vague result which will be improved once your Interferometer is assembled and steadily pointing at a distant viewing screen.
If everything works, put your Laser module to the side.
Step 5: Assemble Laser Mount
We'll need our laser to sit straight and horizontally level for the best results.
We will insert the Laser in the PVC and mount the PVC in the end of the project enclosure.
First, measure placement for a hole to allow the Wires from the Laser to pass through. To do this, drill a hole and smooth the edges with your sanding bit. Use the sanding bit at an angle to avoid kinked wires.
Next drill a centered hole in the side or end of your Project Enclosure. I used a tall box on it's side to allow removal of the lid and mounted the laser there for easy access. The hole should be large enough for the Pipe to fit through but not the Cap, which, with a little glue, will hold it in place.
Apply glue, hold straight, apply pressure and allow glue to dry.
Lastly, drill another large hole with your Hole Punch Bit centered on the end across from your laser for the light to exit the box. Then, drill a hole in your Ramekin or cap and glue it around the hole you just drilled to cover the rough edge and signify where the light will exit.
Step 6: Assemble All Components
Now its time to put everything together!
Glue the Battery Holder somewhere on your project enclosure that is convenient and close enough to the Laser for the wires to connect. Depending on your Enclosure, you may need to drill a small hole for the wires at this point as well.
Your Laser mount should now be dry and solid, so, insert the lead wires for your Laser into the PVC pull them through the hole you drilled and press the Laser in behind it until it is snug and straight.
Next, feed the Battery leads into the Enclosure, connect to Laser and close the box or attach the lid depending on your particular enclosure. Finally, cut out and attach the warning label from your Laser onto your Interferometer for safety.
Step 7: Your Interferometer Is Complete!
Your Interferometer is now complete! Flip it on and make sure everything works before we begin our experiments!
Step 8: Hypothesize: What Happens If Particles Pass Through Two Slits?
To put your new Interferometer to use we will be performing one of the most important experiments in all of science. Upon performing this experiment, we will be able to answer one of the most prevailing questions in physics.
What is light? Is it a particle or a wave?
To answer this question, let us hypothesize what light will do when it passes through two slits. To do so, let's consider the following.
If particles are propelled through two slits? What will happen? How will they react on the other side? Let's find out!
To find out what happens when particles pass through two slits we will consider this. If we take a piece of board and cut two slits in it and place it in front of a clean surface, what will happen if we spray particles of, say, spray paint at those two slits? Try for yourself or see the images for the result. When particles pass through the slits the particles are split into two groups which appear as two marks on the surface behind the slits, as shown above.
Step 9: Hypothesize: What Happens If a Wave Passes Through Two Slits?
Now lets think about what happens if a wave passes through two slits. If one wave passes through two slits, two identical waves will emerge on the other side from their respective slits. Let's see if we can identify any characteristics from this event.
First, let's observe one wave on its own in the first image above. Next, by simultaneously making two waves of equal wavelength and magnitude we can observe how they interact. Since they are identical and in phase this is analogous to the output of our Double-Slit Experiment. What we find is that along any line perpendicular to the direction of travel we see a series of waves, troughs and flat areas. The flat areas occur when one's crest intersects with the other's trough, cancelling each other out. The only way this can occur is if it is two oscillating waves, areas of high and low pressure, moving through a substance and not actual directional motion of the substance itself.
Step 10: Hypothesize: What Happens If Particles Moving in a Wave Passes Through Two Slits?
The question has been poised, "Is light a particle or a wave?" But, light has been proposed to be particles moving in a waveform. Now let's see what happens when particles moving in a wave pass through our double slit from earlier.
With our double slit and a screen placed behind, we will again spray a stream of particles through the slits but this time the particles will be moving in waves on the x, y and z axises in three separate experiments, respectively. We will also remember the results of our linear particles moving through a double slit as our control experiment, then we'll move the source on the x-axis, then on the y and finally on the z-axis. When we're done, we'll compare the results.
Let's begin! My results can be seen in the attached images.
What we find is that when the particle source is still, it results in a pattern on the other side of the slits that very much resembles the shape of the slits, as we'd expect, as we saw in Step 8.
When the source of particles is moving on the x axis (left to right) a wave on the x axis is created over time which results in a slightly wider pattern on the screen behind.
When the source of particles is moving on the y axis (up and down) a wave on the y axis is created over time which results in a slightly taller pattern on the screen behind.
When the source of particles is moving on the z axis (back and forth) a wave on the z axis is created over time, the results of which are insubstantial as compared to our control experiment.
Note that in none of these instances does an interference pattern appear; that would be impossible.
Step 11: Perform Double-Slit Experiment
Now with our Double-Slit Interferometer we can pass a single light through two slits and out will emerge two bands of light. What do you think the light will most closely represent in this instance? Will the light emerge as two groups as the particles of spray paint did? Or will the light emerge as a interference pattern, a series of wave, cancellation, wave, cancellation, wave, cancellation, etc.?
Let's dim the lights, flip on our new Double-Slit Interferometer and find out! Turn on the laser and point the light at a smooth, non-reflective surface. What do you see?
What we see is nothing like passing particles through two slits! We see a clear interference pattern! If light were particles they would build up in two distinct areas, not cancel out! What we are seeing are the multiple "ripples" of the light wave with clear interference patterns where the "ripples" intersect. The only way that this can occur is if light is not particles;
LIGHT IS A WAVE!!!
Step 12: Conclusion: Light Is a Wave!!!
Congratulations! With this experiment you just unequivocally and without a shadow of doubt proved that light is a wave!
It makes sense, though. Right? Light is measured in "wavelength." Changing the wavelength changes the properties of the light (i.e. color, etc.). When an electric light bulb emits light, it is not emitting particles; it is emitting a variation of the wave of electricity from which it is supplied.
What are the implications of what we just learned? What you will realize is the paradigm-shifting reality of the nature of our universe and our place in it.
What about all this talk about the "wave-particle duality of light"? Well, like we discussed earlier, "As we know, these are not mutually exclusive characteristics. “Particle” describes the composition of a substance and “wave” describes the motion of it." We obviously don't ask, "Is the ocean made of water or waves?" It's a foolish question because we can see what the ocean is; it is water moving in the form of waves. Now, after this experiment, we can similarly see what light is.
So, what about the "evidence" that light is a particle? Pressure of light experiments show that emitting a light on a lightweight, balanced object can propel it; but this could be explained by the heat differential creating thermal expansion on the side of the object which the light wave is projected, no "photons" necessary. If light is a wave then it needs something to pass through, right? The Michelson-Morley experiments aimed to prove just that. They were unable to detect the motion of such a substance, which they referred to as aether; they did not however disprove its existence. What do you think that means?
These and many more have been explained by the particle nature of light theory, which has just been proven to be incorrect. So what substance do light waves vibrate through in space? How does the sun's light reach us?
What about Einstein? The invention of the idea of the photon was developed progressively by Albert Einstein over the course of his career to purportedly elucidate experimental observations that he could not explicate by the classical wave theory of light. By overtly dismissing the long standing equations of James Clerk Maxwell, albeit apparently minutely, novel profusions of models were able to emerge. These models, though, were dependent on the inconsistent assumptions stated in Albert’s 1905 "On the Electrodynamics of Moving Bodies,” his Theory of Special Relativity ,which postulates that, “light is always propagated in empty space with a definite velocity c.” Einstein defined light as "composed of 'photons;'" matter that moves at the speed of light. Particles of any mass, no matter how minute, would have the momentum to displace anything in its path, including out planet's atmosphere. So how did old Albert explain this? He said photons were a mass-less particle with momentum. Well, any student of physics knows this is impossible, because p=mv; if mass is zero, momentum is zero! Looks like Einstein needed a refresher on basic physics! On this fact, among many others, relativity falls apart completely. Einstein had it wrong. He never bothered to perform experiments which precluded him from seeing the truth.
"No amount of experimentation can ever prove me right; a single experiment can prove me wrong."
Newton had it wrong, too.With these findings the implications are endless! If light is a wave, as we now know it is, it must need a substance to pass through. What is this substance of which we are at the center? Can we apply this new found knowledge to "electricity" as well? Does that mean electricity does not require "free electrons" and can be transmitted wirelessly? If light is not a particle does that explain the photo-electric effect? Is the vibration of light simply being converted to a different frequency? What questions do you have? I know I had plenty which are being answered in my upcoming book tentatively titled, "Quantified Unification of Energetic Sub-Atomic Particles." Leave your questions in the comments and let the inevitable debate begin!
“I will never have greater respect than for the man that realizes he was
wrong and graciously admits it without a single excuse.”
"It Is Easier to Fool People Than to Convince Them That They Have Been Fooled."
Step 13: Ask Questions! [FAQ]
Q: Isn't light a particle and a wave? That's what Wikipedia says...
A: Based on the definitions of "particle" and "wave" 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. Don't take Wikipedia's word for it. Try the experiment for yourself and let us know what you find.
"People's beliefs and convictions are in almost every case gotten at second-hand, and without examination, from authorities who have not themselves examined the questions at issue but have taken them at second-hand from other non-examiners, whose opinions about them were not worth a brass farthing." - Mark Twain
Q: I thought light was neither a particle or a wave. Isn't light a quanta?
A: Again, let's examine our definitions, defining light as quanta is incomplete to say the least. "Quantum", plural "quanta," is defined as the following: "a particular amount". And, with reference to Physics: "the smallest quantity of radiant energy, the fundamental unit of a physical magnitude."
When asked what kind of car you drive, you wouldn't answer, "2400 lbs" or "200hp," I hope.
Q: Hasn't an interference pattern been detected with electrons, whole atoms and particles?
A: The question of the Merli-Missiroli-Pozzi and Feynman two-slit electron Experiment experiments where it is purported that “electrons” can pass through a double slit and result in an interference pattern has been brought up several times. If we are to base our entire scientific view on a few iterations of a single experiment, then we should examine that experiment closely and hold it to a higher standard.
By reviewing their experiments and examining the instruments with which they were performed, we will find that in any case that yields the ostensible result; the charged “electrons” are being propelled by way of an electromagnetic field. Firstly, it is this charge that moves the electrons and therefore propels them only along the wavelength of this electromagnetic wave. Additionally, it is also essential to note how the “electron” pattern data is collected, by electromagnetic means. Consequently, this experiment's results cannot therefore be replicated in such a way that isolates the particles and is therefore invalid.
In order to validate this experiment, it can be performed as follows: Perform the test in a similar experimental environment but with the following adjustments. In order to propel the “electrons” in a way which isolates them from any outside electromagnetic wave, propel the electrons by way of a linear mechanical force of your choosing. This will validate the non-isolation errors of these previous experiments. Next, in recording of the data non-isolation errors can occur as well, therefore retrieval of data should be isolated to non-electromagnetic means, preferably mechanical, as well. By performing the experiment with these errors resolved, it is then only the particulate electrons that are being isolated in the experiment and output data.
In any and every occurrence wherein these non-isolation errors have been resolved, no interference pattern can be detected.
It is easy to see how confusion can occur on micro and nano levels, however. That is why is is so important, crucial in fact, to observe and examine the natural world around us. Mathematics can be written to any end, experiments outside our realm of sensory perception are riddled with potential areas for error. We must look at the stars in the sky, the waves of our oceans and perform simplistic experiments with no room for error or misinterpretation, such as this.
Q: Well then, have you written the math to support this?
A: Fortunately, it's not a new model so 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.
Q: Can you explain the photo-electric effect without particles?
A: I'd be glad to. The photo-electric effect, on which Einstein received his
Nobel, is proposed to be caused by particles ("photons") causing other particles ("electrons," specifically "free electrons") to be emitted. If we can show an electromagnetic wave passing through a medium which is non- metallic in nature and void of "free electrons," and being transmitted as usable "electricity", the "free electron theory" and subsequently the particle explanation of the photo-electric effect will both be invalidated.
... and here we have it: https://cdn.instructables.com/FJK/DXXZ/I7IVTEM0/FJK...
One of the possibilities unveiled by the wave theory of all electrodynamic phenomenon, and discarded by the the particle theory, is wireless transmission of electricity, as you see here. Wireless transmission of electricity is congruent with neither Al's 1920 work nor his postulates published in 1921.
Q: Isn't there other "evidence" of the particle nature of light?
A: All things considered, there isn't much.
After finding the obvious flaws in the Pozzi and Feynman experiments there are only a few other things to consider.
One of which that comes to mind is the Michelson-Morley experiment and ones like it which only fail to detect the motion of a substance through which light waves can pass; they do not disprove the existence of it.
Pressure of light experiments and the functionality of devices like the Crookes Radiometer can be simply explained by by the heat differential creating thermal expansion on the side of the object which the light wave is projected, no "photons" necessary.
Q: You are kidding, right? Einstein, Feynman, Heisenberg, Bohr all wrong?
A: You forgot Newton. He was wrong too. Discouraging, at first, I know, but encouraging in the end. The implications open a world of possibilities.
But, Maxwell, Faraday, Tesla, Airy, Michelson, Morley, Sagnac were all on the right track. That is why all of the formulas and technology that are used in practical applications every day were written and invented by these guys.
This experiment has been performed countless times with innumerable variations, always with the same result. Furthermore, never in a million trials of a million variations can particles create an interference pattern. Never. It's impossible. As this experiment and others like it show, only waves can produce interference, cancel each other out. Particles can only be added (1+1=2), only waves moving through substance can cancel each other out (-1+1=0). Not a particle, not particles moving in a wave, only a wave of oscillating vibrational energy can have this effect. Try the experiment and see for yourself!
Q: Light used to travel through the aether. But due to budget issues that program was shut down by the US government in the 1920s. Now light has to travel through vacuum. Right?
A: That explanation makes far more sense than most of the others I've heard!