Light Emitting Diode (LED)

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  Light Emitting Diode (LED) Introduction A Light Emitting Diode (LED) is a semiconductor device that converts electrical energy directly into light energy. It is a special type of PN junction diode that emits light when it is operated in the forward-bias condition . LEDs are widely used in electronic and electrical systems because they are small in size, consume less electrical power, have a long operating life, and can produce light in different colours. Common applications of LEDs include: Indicator lamps Digital displays Traffic signals Remote-control systems Automotive lighting Decorative lighting Street lighting Electronic instruments Television and computer displays Optical communication systems The basic principle behind LED operation is electroluminescence .   What is an LED? A Light Emitting Diode is a PN junction semiconductor device that emits visible or invisible light when current flows through it in the forward direction. T...
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Di atomic lattice

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 Di atomic lattice

A Diatomic lattice is a crystal structure whee the repeating unit contains two different atoms instead of just one.

Simple explanation
  • Mono atomic lattice- same atoms (AAAAAA........)
  • Di atomic lattice - (ABABAB......)

Diatomic Lattice (Two-Atom Lattice)


A diatomic lattice is a crystal lattice in which:

ü  Each unit cell contains two different atoms

ü  The atoms have different masses (m₁ and m₂)

They are arranged alternately in a periodic structure

 Example pattern:
m₁ — m₂ — m₁ — m₂ — m₁ — m₂

Image is AI illustration

Di atomic lattice is
contains two atoms per unit cell.
Atoms arranged in periodic pattern.
Can be ionic or covalent crystals.
Important in semiconductors and solid state physics.
Shows optical and electrical properties due to two atoms.


Structure

In a diatomic lattice
Each unit cell has two atoms.
These atoms  can be:
Same element but different positions.
Different elements (more common).


Examples

Some common diatomic lattice type crystals:
Sodium Chloride- Na and Cl atoms alternate.
Zinc Sulfide- Zn and S atoms.
Gallium Arsenide-Ga and As atoms.

 Uses and Applications:
Used in semiconductor.
Important for electronics and chips.
Helps understand vibrations( phonons) in solids.
Used in Optical devices.




Acoustic Mode

Atoms move in same direction (in phase)

Frequency is low

At k=0k = 0k=0, frequency = 0

 Similar to sound waves 

 Optical Mode

Atoms move in opposite directions (out of phase)

Frequency is high

Even at k=0k = 0k=0, frequency ≠ 0

 This is why it is called "optical" .


In physics, diatomic lattices are used to study

Acoustic and optical modes of vibration.

This explains how heat and sound travel in Solids.

 

Vibration Behaviour

The relationship between angular frequency-ω

Wave vector –κ

ω2=β(1/M1+1/M2)± β√(1/M1+1/M2)2-4sin2(ka)/M1M2

β-Force constant

M1M2-atomiic masses

a-Distance between adjacent atoms 


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