Published in

Jungletronics

# Diffraction: Classical Wave Behaviors

## Collection of all the links I used to understand the subject — Collection Episode #00

Hi, in this page I will try to guide you through the fundamentals behind light.

We will use a awesome simulator here, too! Be tuned!

If you are in a hurry, see this vid: Diffraction (Young’s Double Slit & Grating) — A-level & GCSE Physics by Science Shorts.

Or this one: The Original Double Slit Experiment by Veritasium.

Or this simulator PhET sim from: PhET — University of Colorado Boulder.

Or this one: ck-12 — Exploration Series — Physics Simulations from interactives.ck12.org (please, create your account, it is amazing! I highly recommend you create and enjoy all science they offer for free :).

Light is a particle or a wave?

Diffraction is the generic name given to phenomena associated with deviations of light propagation in relation to predicted by geometric optics (i.e. Rectilinear Propagation of Light) and which reveal the light’s nature wave instead of a corpuscular matter.

Diffraction phenomena are observed for all types of waves. Rarely we observe the diffraction of light in everyday life. Nonetheless, the diffraction of sound waves is difficult to avoid; the sound bypasses relatively large obstacles, such as people, trees, and furniture in a living room. This difference between the diffraction of sound and light is due to the difference between the respective lengths wave. The wavelength of sound is of the order 1 m, while that of visible light is on the order of 500 nm.

For centuries scientists are debating over this issue. The wave-particle duality.

The Dutch physicist Christiaan Huygens (1629–1695) was one of the first to systematizes of the wave theory of light, in opposition to their contemporary Englishman Isaac Newton (1642–1727), the who attribute the defense of a theory purely corpuscular.

The corpuscular theory of light, based on the Greek idea of atomism of antiquity, describes that light is composed of discrete particles called “corpuscles”, which describe a trajectory in a straight line, with limited speed.

The wave theory states that light is a wave, just as sound propagation. This wave model was based on the famous Experiment by Thomas Young (1773–1829), known as The Double Slit Setup, carried out in 1801, which involved the phenomena of diffraction and interference of light, object of this study.

Welcome o/

Let’s get started!

Think about harbor wall. If you have a harbor wall and waves are coming in, like here:

The walls is going to stop a lot of the wave fronts but when they go through the aperture the waves don’t just carry on as little waves here but no they’re going to spread out like that Photo 2. That’s what we call diffraction when waves go through a gap or around an object they diffract they will fill in the empty space where the waves aren’t. This is incredible \o/

Hint: See these vids series from OpenLearn from The Open University: Properties of Waves — Exploring Wave Motion (1/5)

## Wave Properties

Amplitude → Human perception of amplitude = loudness or volume;

Wavelength → 𝝀 { \lambda };

Frequency → Human perception of frequency = pitch (compasso in Portuguese, I guess…) or vibration.

## What is volume and pitch?

Volume is a measure of how loud or soft something sounds and is related to the strength of the vibrations (amplitude related). Pitch is a measure of how high or low something sounds and is related to the speed of the vibrations that produce the sound (frequency related). The sound is caused by vibrations (back and forth movements).

## Fundamental Equation 4 Wave Propagations

google harbour wall waves diffraction and you’ll see a lot of mind-boggling examples; try it now!

An this diffraction is related with the wavelength. Look…

As you can see narrow gap tends to diffract more, right?

Sounds diffract like wave. That’s awesome!

Remember that the diffraction is related to the wavelength (Photo 2). When the dimensions of the aperture have the same proportions of the width (amplitude) of the wave, then we can perceive this phenomenon. In our daily lives, we do not have this privilege, as the dimensions of obstacles are much larger than the dimensions of light waves. Look, just about the light, not about sound, that diffract easily (Fig. 1).

Thomas Young — Double Slit setup (1801) states that this is the behavior of light. This explain why the man behind the wall can hear his pursuer’s footsteps on the dark side of the hall (Fig. 1).

Monochromatic light means one wavelength, constant phase difference. Laser nowadays is used instead of candles, and this is how we get the same effect generally we use red light and reddish light.

If the path difference is half a wavelength what does that mean means that the waves actually arrived pi radians or 180 degrees out of phase they don’t constructively interfere they destructively interfere; they cancel each other out and we end up with a dark spot.

There is a constructive interference because the rays arrive in phase; if the path difference however is a multiple and a half of the wavelength then that means that the waves are going to arrive out of phase pi radians 180 degrees out of phase so that means that you end up destructive interference so that’s when you get a dark fringe. That’s the patterns you see in Fig. 5 above (fringes).

Constructive interference you end up with a bright fringe; dark fringes are because of destructive interference.

Diffraction from a single slit results that the interference central maximum is very intense, very bright compared to the other fringes and also it is double the width of the fringes too (Fig. 7).

Now about Young Double Slit setup observe that the central waves are much thinner and the fringes are much closer together (Fig. 8).

Diffraction grating (not shown here) is different to Young’s double slit instead of just having two slits like that instead we got lot and lot of slits that are very very small and we get lots and lots of diffraction happening when light passes through that and deflect afterwards diffract as it goes through this is where we can’t use.

## Virtual Simulator — Algetec — Brazil

From now on we will use of the Algetec Simulator, which is a virtual laboratory that simulates the real environment and allows the student to carry out experiments without leaving home. Replicas with a high degree of fidelity to the traditional physical laboratory.

For all experiments we will follow the following Virtual lab procedures:

1 — Turn on the laser;

2 — Choose the emitter light wavelength:

3 —Change the Diffraction Grid distance — obstacle to the beam light;

4 — Turn off the laboratory light;

5 — Check the gap distance between the grade and the screen;

6 — View the formed fringes;

7 — Determine the wavelength of the corresponding light;

8 — Experiments nº2 to nº5 — Determination of wavelength of other colors: Orange, Yellow, Green and Blue incidents — Slot option “Fio de Cabelo” [Wire of hair];

9 — From now on (Experiments nº6 to nº10) we will modifying the Slit Size — First Red Laser:

## Conclusion

The potential of using simulators such as demonstrated in this work, Algetec simulators, has a huge potential use in modern education.

We hope that this work, carried out with the greater care and technical rigor, can serve Guide for the Computer Engineer in Brazil and in Physical Optics and in the World.

That’s it!

See you soon ! Have a nice day.

Bye! o/

👉 doc: calc. memories

👉 doc: in portuguese

# Credits & References

For Young’s double slit equation See all these links to get the big picture about light:

Wave refractions by Keith Meldahl

Solutions for Engineering courses by Algetec

Quantum Mechanics: Animation explaining quantum physics by Eugene Khutoryansky

Difração by mundoeducacao

Difração by wikipedia

Difração da luz por fendas by Hugo L. Fragnito and Antonio C. Costa Unicamp-IFGW, Março de 2010

Ondas e Ótica — Uniasselvi by Prof. Jaison Rodrigo da Costa. Profª. Liana Graciela Heinig. GABARITO DAS. AUTOATIVIDADES

Most likely you will not follow the clues to understand about the nature of light.

However, I decided to register all the pages I visited to understand the subject.

Who knows, in the future, it will be able to better organize the resources to make more sense in a way that led me to publish a report:

--

--

## J3

Hi, Guys o/ I am J3! I am just a hobby-dev, playing around with Python, Django, Lego, Arduino, Raspy, PIC, AI… Welcome! Join us!