The Real Double Slit Experiment.

Summary

This video offers an in-depth look at the double slit experiment, a classic physics demonstration with a twist. Unlike most videos that only discuss the experiment, this one showcases the actual setup and results. The creator uses slits as narrow as a few wavelengths of light, allowing for detailed observation under a microscope. The video reveals the intricate interference patterns that emerge when light passes through the slits, highlighting the experiment's complexity and beauty. It also details the process of creating the slits using lithographic photomasks and demonstrates the experiment with both green and red lasers, showcasing the fascinating details of quantum mechanics.

Takeaways

• 🎥 The video presents a unique take on the double-slit experiment, showcasing actual experimental footage instead of just discussions.
• 🔬 The experiment uses slits with a width of only a few wavelengths of light, which is narrower than most traditional experiments.
• 🔍 The study of the experiment is conducted under a microscope, allowing for a more detailed observation of the diffraction patterns.
• 🛠️ The creator made various slits ranging from 2.5 to 25 microns and varied the distance between them for the experiment.
• 📸 The video shows the cross-section of a laser beam passing through slits, resulting in an interference pattern of bright and dark bands.
• 🌟 The individual slits produce an interference structure before their light visibly interacts with the other, which is a key detail of the experiment.
• 📈 The interference pattern develops between the slits and is different from what would be expected if the intensities were simply added together.
• 👨‍🔬 The experiment is conducted using old lithographic photomasks, a photoresist layer, and UV-light exposure to etch the slits.
• 💡 Two types of lasers were used in the experiments: a green laser diode and a red helium-neon laser, with the latter having better beam quality.
• 🔭 The experimental setup includes a microscope that projects the light from the slits onto a camera's CMOS chip for detailed observation.
• 📹 The video demonstrates that the double-slit experiment has many fascinating details that are often overlooked in standard presentations.

Q & A

What is the main purpose of the video?

The main purpose of the video is to demonstrate the double slit experiment in a unique way, showing the actual experiment rather than just talking about it, and to explore the experiment's details with greater precision using very narrow slits.

Why is the double slit experiment significant even after more than 200 years?

The double slit experiment is significant because it demonstrates fundamental principles of quantum mechanics and wave-particle duality, which continue to be relevant and studied for a deeper understanding of the physical world.

What makes this video's version of the double slit experiment different from most others?

This video's version of the experiment uses slits with a width of only a few wavelengths of light, which is significantly narrower than those used in most experiments, and studies the diffraction under a microscope rather than at a large distance on a screen.

What range of slit widths were used in the experiment?

The experiment used various slits ranging from 2.5 to about 25 microns in width.

How did the presenter vary the experimental conditions?

The presenter varied the distance between the slits and used different lasers (a green laser diode and a red helium-neon laser) to study the diffraction patterns.

What is observed when a laser beam passes through the narrow slits?

After passing through the slits, the light spreads out in bright and dark bands, particularly in the direction perpendicular to the slits, showing an interference pattern that develops between the slits.

What is the scale at which the observed phenomena occur?

The phenomena observed in the experiment happen within a scale of 1 cubic millimeter.

How does the interference pattern from the double slits differ from individual slits?

The interference pattern from the double slits is quite different, showing a complex structure that develops between the slits and spreads out over the entire pattern, unlike the uniform bump that would result from simply adding the intensities of individual slits.

What materials and techniques were used to create the slits for the experiment?

The slits were etched using old lithographic photomasks, a photoresist layer exposed with UV-light in the pattern of the slits, and the chromium underneath was etched to create tiny transparent slits in the chromium layer.

How was the measurement setup arranged for the experiment?

The setup included a laser source (either a green laser diode or a red helium-neon laser), a disk with etched slits placed on a microscope table, a microscope to project the light onto a CMOS chip of a camera, and a beam splitter for directing the HeNe-laser's beam.

What was the role of the DIY maskless wafer stepper in the experiment?

The DIY maskless wafer stepper was used to produce the exposure patterns in the photoresist, which were essential for etching the desired slit patterns in the photomasks.

Outlines

00:00

🧪 Introduction to the Double Slit Experiment Video

The video introduces the double slit experiment, a classic physics experiment with a history of over 200 years. The creator acknowledges the abundance of videos on the subject but emphasizes their unique approach. Instead of just talking about the experiment, the video will showcase the actual experiment with a focus on the details. The creator's version uses slits with a width of only a few wavelengths of light, which is narrower than most experiments. The setup involves studying diffraction under a microscope for a closer look. The video will cover the setup, execution, and the intriguing details observed during the experiment.

🔍 Detailed Observation of the Double Slit Experiment

This paragraph delves into the specifics of the experiment's observation. The creator made various slits ranging from 2.5 to 25 microns wide and varied the distance between them. The video shows the cross section of a laser beam passing through two narrow slits of approximately 3.5 microns, resulting in a pattern of bright and dark bands. The individual slits produce an interference structure before their light visually interacts. As the distance increases, the light from the two slits begins to interact, creating a complex interference pattern. The video includes an intensity profile graph, demonstrating the sum of pixel column intensities and how the pattern develops. The experiment is presented as a real-world demonstration, not a simulation, to highlight the fascinating details of the double slit experiment.

🛠️ Fabrication and Setup of the Double Slit Experiment

The creator describes the process of fabricating the slits used in the experiment. Old lithographic photomasks were used, with a photoresist layer etched using UV-light in the pattern of the slits. The photoresist was developed, and the chromium underneath was etched to form tiny transparent slits. The exposure patterns were produced using a DIY maskless wafer stepper, previously featured in the creator's videos. The measurement setup involved two different lasers: a green laser diode and a red helium-neon laser. The green laser required collimation with a lens, while the HeNe laser used a beam splitter. The slits were etched on a disk on the microscope table, and the microscope's objective projected the light onto a CMOS chip of a camera.

Keywords

💡Double Slit Experiment

The double slit experiment is a classic physics demonstration that explores the wave-particle duality of light and matter. It involves sending a beam of light through two closely spaced slits and observing the resulting interference pattern on a screen. In the video, the experiment is conducted with very narrow slits, which is significant as it allows for a more detailed examination of the diffraction and interference phenomena.

💡Diffraction

Diffraction refers to the bending of waves around obstacles or the spreading out of waves after passing through an aperture. In the context of the video, diffraction is observed when light passes through the slits and begins to spread out, forming the characteristic pattern of bright and dark bands. The video emphasizes studying diffraction under a microscope for a closer look at the process.

💡Wavelength

Wavelength is the distance between two consecutive points in a wave that are in the same phase, such as from one peak to the next. The script mentions that the slits used in the experiment have a width in the order of only a few wavelengths of light, which is narrower than typical setups, and this detail is crucial for observing the fine details of the diffraction pattern.

💡Microscope

A microscope is an instrument used to observe objects that are too small to be seen by the naked eye. In the video, a microscope is utilized to study the diffraction and interference patterns created by the double slit experiment in greater detail, as opposed to observing the patterns at a large distance on a screen.

💡Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of radiation. In the script, two types of lasers are mentioned: a green laser diode and a red helium-neon laser. These lasers are used as light sources for the double slit experiment, with the helium-neon laser noted for its better beam quality.

💡Interference

Interference is a phenomenon in which two waves superpose to form a resultant wave of greater, lower, or the same amplitude. In the video, the interference pattern develops between the slits, showing how the light from each slit interacts and combines to create a pattern that is different from simply adding the intensities of the individual slits.

💡Intensity Distribution

Intensity distribution refers to the variation in the strength or brightness of a wave, such as light, across a given area. The video script describes observing the intensity distribution of a laser beam's cross section after it passes through the slits, which helps in understanding the formation of the interference pattern.

💡Photomask

A photomask is a photographic plate or glass plate used to transfer a pattern onto a semiconductor during the process of photolithography. In the script, old lithographic photomasks are repurposed to create the slits for the double slit experiment, demonstrating a creative use of existing materials for scientific exploration.

💡Photoresist

Photoresist is a light-sensitive material used in photolithography to create a pattern on a substrate. The script describes using a photoresist layer that is exposed to UV light in the pattern of the slits, which is then developed to etch the desired pattern into the chromium layer, resulting in the transparent slits used in the experiment.

💡Etching

Etching is a process used to create designs on a hard surface by cutting into it. In the context of the video, etching refers to the process of creating the slits in the chromium layer after the photoresist has been developed, which is a crucial step in preparing the slits for the double slit experiment.

💡CMOS Chip

A CMOS (Complementary Metal-Oxide-Semiconductor) chip is a type of integrated circuit technology used in digital cameras to capture images. The script mentions that the microscope's objective projects the light onto a CMOS chip of a camera, which is essential for recording and analyzing the results of the double slit experiment.

Highlights

Introduction of a unique take on the double slit experiment, emphasizing the presentation of actual experiment footage rather than just discussions.

Use of slits significantly narrower than typical experiments, with widths in the order of a few light wavelengths.

Studying diffraction under a microscope for detailed observation, instead of at a large distance on a screen.

Creation of various slits ranging from 2.5 to 25 microns wide for the experiment.

Variation of the distance between the slits in the experiments for different outcomes.

Visual demonstration of the cross section of a laser beam showing the intensity distribution through narrow slits.

Observation of light spreading out in bright and dark bands, particularly perpendicular to the slits.

Explanation of the non-uniform spreading of light due to the scale of observation within 1 cubic millimeter.

Detailing the interference structure present in the pattern of an individual slit before interaction with the other.

Description of the gradual interaction of light from two slits as they move further apart.

Presentation of an intensity profile graph showing the sum of pixel column intensities.

Highlighting the development of the interference pattern between the slits, starting at the center and spreading out.

Measurement of the interference pattern, showing differences from simply adding intensities of individual slits.

Emphasizing the experimental nature of the demonstration, distinguishing it from simulations.

Use of old lithographic photomasks and photoresist layer for etching the slits with UV-light.

Description of the DIY maskless wafer stepper used for producing exposure patterns in the photoresist.

Explanation of the measurement setup using two different lasers: a green laser diode and a red helium-neon laser.

Comparison of beam quality between the green laser and the helium-neon laser, with the latter being better.

Description of the light collimation process using a small lens and projection onto the etched slits.

Detailing the use of a beam splitter for directing the helium-neon laser beam towards the slits.

Setup of the microscope on the other side of the slits to project light onto a CMOS chip camera.

Transcripts

Hello everybody, This video it about the double slit experiment

and maybe you wonder why someone wants to make yet another video about a more than 200

years old experiment.

Especially with already tons of videos on YouTube regarding the subject.

Well, for one: most videos don't show the experiment, but just show you people talking

about it.

But in this video, we will have a look at the real deal.

And, because I show you my own version of the experiment, there is a good chance that

My version of the experiment uses slits that have a width in the order of only a few wavelengths

of light, which is actually significantly narrower than used in most experiments.

And we will study diffraction under a microscope instead of at a large distance on a screen.

This allows us to look at a few aspects of the experiment with much greater detail.

So, to perform the experiment, I made various slits ranging from 2.5 to about 25 microns.

And in the experiments, I also varied the distance between the slits.

So let me first show you what you actually see in the experiment, and after that, let's

have a look at how the experiment works and how the images were made.

Here we are looking at the cross section of a laser beam showing the intensity distribution.

This beam is sent through two very narrow slits of approximately 3.5 microns wide.

And this is what you observe after the light has passed the slits.

It spreads out, in these bright and dark bands, especially in the direction perpendicular

to the slit.

By the way, notice how the individual slits are not spreading the light as a uniform bump.

And this is because of the scale at which we're observing, Basically, everything you

see here happens within 1 cubic millimeter.

You can see that the pattern of an individual slit already contains a lot of interference

structure before its light starts to visually interfere with that of the other slit.

As we move further away, the light of the two slits gradually starts to interact.

Here at the bottom, you see an intensity profile plotted and this graph shows you the sum of

intensities of the pixel columns in a part of the image above the graph.

Now notice how the interference pattern develops between the slits, first there in the center,

and later spreads out over almost the complete extend of the pattern.

You can actually measure that the interference pattern is quite different from the patterns

you would get if you would just add up the intensities of the individual slits.

What you see here is all experimental and is not just some simulation.

And I wanted to show you this first, to demonstrate that the double slit experiment actually contains

way more fascinating details than are normally presented.

used old lithographic photomasks for this purpose.

To etch the patterns, I used a photoresist layer, and exposed this layer with UV-light

in the pattern of the slits.

After that, the photoresist was developed and chromium underneath was etched in the

desired pattern.

The result is tiny transparent slits in the chromium layer.

By the way, the exposure patterns in the photoresist were produced by using the DIY maskless wafer

stepper that featured in several of my previous videos.

And here is the measurement setup.

For the experiments I actually used 2 different lasers: a green laser diode and a red helium

neon laser.

They both worked fine.

However, generally the beam quality of the Helium Neon laser was a bit better.

When using the green laser, light was collimated with a small lens and then projected on the

slits, which were etched in this disk placed on the table of the microscope.

In the case of the HeNe-laser I just used a beam splitter to direct the beam upward

towards the slits.

On the other side of the slits is the microscope that can be moved from and to the slit pattern.

And the objective of the microscope projects the light on the CMOS chip of a camera, which