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Page 6 of 13 — articles on the physics of light, sorted newest first.
Electron & Neutron Diffraction: How Matter Waves Reveal Structure
Electron diffraction is the wave-like scattering of electrons by crystalline materials, proving that matter has wave properties. When a beam of electrons is accelerated through a potential difference and directed at a thin crystal, it produces a diffraction pattern — exactly like X-rays or light. This is a direct consequence of wave-particle duality: every particle has a de Broglie wavelength λ = h/p, and when that wavelength is comparable to atomic spacings in a crystal, diffraction occurs. Here is how electron diffraction works, the experiments that proved it, and how it is used in techniques like TEM, LEED, and neutron diffraction.
Fraunhofer Diffraction vs Fresnel: 5 Essential Differences
Fraunhofer diffraction (far-field) and Fresnel diffraction (near-field) are two regimes that describe how diffraction patterns change with distance. In Fraunhofer diffraction, the source and screen are effectively at infinity, giving planar wavefronts and a stable pattern. In Fresnel diffraction, the source or screen is close to the aperture, giving curved wavefronts and a pattern that changes with distance. The Fresnel number N_F = a²/λL tells you which regime applies. Here is the difference, the maths, and when to use each.
Laser Diffraction & Particle Size Analysis: The Lab Guide
Laser diffraction measures particle sizes by analysing how a laser beam scatters off particles in suspension. Large particles scatter light at small angles; small particles scatter at large angles. By measuring the angular intensity pattern of the scattered light and applying Mie theory or the Fraunhofer approximation, a laser diffraction particle size analyser calculates the full particle size distribution — from tens of nanometres to several millimetres — in less than a minute. Here is how it works, the theory behind it, and what the results mean.
Single Slit Diffraction: 3 Essential Equations & Pattern
Single slit diffraction produces a pattern of bright and dark fringes when light passes through a narrow opening. The central maximum is twice as wide as the others and contains most of the light. The dark fringes follow a sin θ = mλ. Here is how the pattern works, how to derive the equation from Huygens principle, worked examples with real numbers, and why single-slit is different from double-slit or grating patterns.
X-Ray Diffraction (XRD) Explained: Crystals, Proteins & Machines
X-ray diffraction (XRD) is a technique that uses X-rays to determine the atomic and molecular structure of crystals. When X-rays hit a crystal, they scatter off the regularly spaced atoms and produce a characteristic diffraction pattern. By measuring the angles and intensities of the diffracted beams, scientists can calculate the positions of atoms in the crystal — revealing the 3D structure of materials, proteins, and even DNA. Here is how XRD works, what Bragg's law means, the machines that do it, and 5 applications you should know.
Constructive vs Destructive Interference: 5 Easy Comparisons
The short answer: constructive interference happens when wave crests align and reinforce each other (louder, brighter, bigger amplitude). Destructive interference happens when a crest meets a trough and they cancel each other out (quieter, darker, smaller amplitude). Which one you get depends entirely on the phase or path difference between the waves. This guide walks through the definitions, formulas, comparison table, and real-world uses of both types.
Destructive Interference Formula: 5 Essential Wave Equations
The destructive interference formula is Δr = (n + ½)λ (path difference equals a half-integer number of wavelengths). The constructive interference formula is Δr = nλ (path difference equals a whole number of wavelengths). Which formula you use depends on what you know — path difference, phase difference, or the experimental setup. This guide compiles all five essential interference formulas in one place, with two worked examples showing exactly how to apply them.
Diffraction vs Interference: 5 Easy Key Differences
Diffraction is the spreading of waves around obstacles or through openings. Interference is the superposition of waves from two or more sources. The simplest way to tell them apart: diffraction involves one wavefront bending around an edge, while interference requires at least two wavefronts overlapping. They produce different fringe patterns — diffraction fringes are unevenly spaced with rapidly decreasing intensity, while interference fringes are evenly spaced with near-constant intensity. This guide compares both phenomena side by side.
Double Slit Explanation: 4 Easy Steps to Understanding
The double slit experiment passes coherent light through two narrow slits to produce an interference pattern of alternating bright and dark fringes on a screen. This pattern, first observed by Thomas Young in 1801, proves that light behaves as a wave. The fringe spacing is given by Δy = λD/d, where λ is the wavelength, D is the distance to the screen, and d is the slit separation. Here is how the experiment works, what the equation means, and how you can try it yourself.
Double Slit Experiment Quantum Mechanics: 5 Easy Facts
The double slit experiment in quantum mechanics reveals that single particles like photons and electrons can behave as waves and interfere with themselves. When we send particles one at a time through two slits, they build an interference pattern over time — as if each particle went through both slits simultaneously. This guide explains wave-particle duality, the observer effect, delayed choice experiments, and what the double slit tells us about the nature of reality.
Interference Patterns: 5 Easy Types & Fringe Examples
An interference pattern is a stable arrangement of bright and dark bands (or loud and quiet regions) created when two or more waves overlap. The pattern is produced by alternating constructive and destructive interference depending on the phase relationship between the waves at each point. Interference patterns appear wherever coherent waves meet — in Young's double-slit experiment, in soap bubbles, in Newton's rings, and in the output of interferometers. Here are the 5 main types and how to interpret them.
Single Slit vs Double Slit: 5 Essential Pattern Differences
A single slit produces a diffraction pattern with a broad, bright central maximum and rapidly dimming side fringes that are unequally spaced. A double slit produces an interference pattern with many evenly spaced, equally bright fringes. The central maximum in single-slit diffraction is roughly twice as wide as in double-slit interference. This guide compares the two experimental setups, shows you how to identify each pattern at a glance, and explains the surprising infinite slit paradox.