Coupled dipole simulation the the scattering of a Gaussian beam from a point particle. The image is divided in two rows of three images each. The top row show the electric field (in blue and red), while the bottom row show the modulus squared of the electric field (in green), which is proportional to the intensity. The three columns show the incident field, the scattered field, and the total field.

#PhysicsFactlet
Scattering VS Extinction
In #Optics, the concepts of scattering and extinction are closely related. So closely related that many people tend to confuse them.

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#PhysicsFactlet
While electrodynamics is well understood, there aren't many scattering problems we can actually solve. A plane wave scattering from a uniform dielectric sphere is one of those few, and the solution was originally found by Gustav Mie in 1908.
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#PhysicsFactlet
A simple finite element simulation of a pulse scattering on a small (but not point-like) dielectric obstacle.
The scatterer behaves approximately as a re is a very faint halo of light going everywhere, but most light gets diffracted into something similar to a Airy Disk.
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You can make movies showing the evolution of the diffracted field as done by @jacopobertolotti.com in this #PhysicsFactlet
bsky.app/profile/jaco...

#PhysicsFactlet
In its simplest form Monte-Carlo integration allows to estimate a area/volume with complicated boundaries by taking a number of samples and looking at which fraction fall inside the object of interest.
🎢🧪⚛️ #ComputationalPhysics

Two white curves on a black background. The first is a circular loop, labelled as "A knot". The second is a overhand knot, labelled as "Not a knot".

#PhysicsFactlet
Sometimes you need to forego the intuitive way to define stuff for the sake of actually being able to do anything useful with those definitions.

#knots 🧪 🎢
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#PhysicsFactlet
A geodesics on a surface is the shortest* curve connecting two points.

*if you know/care what goes in this footnote, you don't need me to explain 😉

#PhysicsFactlet
The most naïve way to integrate (ordinary) differential equations, is to use the instantaneous velocity to update the position, and the instantaneous force to update the velocity (Euler method). While this is simple and intuitive, it accumulates errors very quickly.
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#PhysicsFactlet
Thanks to some humidity in the air the air flow around the plane wing is clearly visible. Instead of just being deflected by the wing, the air flow tend to stick to the wing (and vice versa), which pulls the wing up and allow the plane to fly.
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#PhysicsFactlet
If evaluating the derivative of your function is not too computationally expensive, one can use the crossing point of the tangent line with the axis as your next best guess ("Newton-Raphson).
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#PhysicsFactlet
The "false position" method works great if the function is roughly linear in the bracketed region, so why don't we multiply by a function (of constant sign, so we don't add spurious zeros) that makes it more linear before applying it?
This is the "Ridders' method"
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#PhysicsFactlet
An improvement over the bisection method is the so-called "false position" method, where instead of dividing the bracket region in two, you cut at the point where the line through the two bracket extremes crosses zero.
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#PhysicsFactlet
The bisection method is a simple and effective way to find the root(s) of a function
The idea is that you start by "bracketing" your root . You then take the midpoint between them, check if your function there is positive or negative and update the bracket.

⚛️🎢 #Computing #Algorithm

Numerical calculation of the radial and angular part of a optical fibre mode. The electric field intensity is shown as a gradient going from black to green, with overlapping tiny black arrows to show the field orientation. The pattern has a hexagonal symmetry and the arrows appear to swirl around the nodes.

#PhysicsFactlet
#PhysicsFactlet
Optical fibre modes are weird but oddly mesmerizing.
#Optics #OpticalFibers

#PhysicsFactlet
Wavefront Shaping is a family of techniques used to control light (or, more generally, a wave) propagating through a scattering medium.

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#PhysicsFactlet
A Shack-Hartmann sensor is a simple and widely used device to measure the phase profile of a wavefront (aka "where the light is coming from").

A mini 🧵
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#Optics #Physics

#PhysicsFactlet
A Stone-Wales defect is a 90 degrees rotation of a chemical bond between two carbon atoms that commonly happens in graphene and fullerene.

#Crystallography #Chemistry #Physics

#PhysicsFactlet
Remake of an old animation about quantum tunnelling in the time domain.
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A few details:
* The incident and reflected wavefunctions interfere, creating fringes when it hits the barrier.
* Even when far away from the barrier, the wavefunction is slowly broadening.

You can make movies showing the evolution of the diffracted field as done by @jacopobertolotti.com in this #PhysicsFactlet
bsky.app/profile/jaco...

Photo of a street on a foggy day. Nearby objects are clearly visible, while objects further away becomes gradually dimmer and blurrier.

#PhysicsFactlet
It's a foggy day here in Albion, so let's talk about light (multiple) scattering!

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🧪⚛️🎢💡 #EverydayPhysics

Photo of a house illuminated by a streetlamp. Due to the mist, the cone of light is well visible.

#PhysicsFactlet
Light propagates in a straight line and we see only the light that comes to our eyes, so you usually don't see the light's path.
Unless it is misty, in which case light can scatter on the water droplets and you can "see" where the light is ("Tyndall effect").
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