What is Planck’s Law
Planck's law, also known as Planck's radiation law.
It describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature.
Spectral density: This refers to the amount of energy emitted per unit wavelength range.
Black body: This is a hypothetical object that absorbs all electromagnetic radiation falling on it and emits radiation based solely on its temperature.
It's a theoretical concept, but it acts as a useful idealization for real objects.
Thermal equilibrium: This means the object has reached a constant temperature without exchanging heat with its surroundings.
Before Planck came along, the existing theories couldn't explain the observed spectrum of black-body radiation accurately, especially at higher frequencies. In 1900.
Energy is not emitted continuously but in discrete packets called quanta.
These packets are named after Planck's constant, a fundamental physical constant.
The energy of each quantum is proportional to its frequency.
This means higher-frequency radiation (like blue light) carries more energy per quantum than lower-frequency radiation (like red light).
Bose’s derivation
Bose's derivation, published in 1924, aimed to explain the black-body radiation spectrum using a novel statistical approach.
This approach differed from classical statistical mechanics and introduced a new counting of states for indistinguishable particles:
Classical mechanics: Assumed particles are distinguishable, leading to an overestimation of high-energy states.
Bose's approach: Recognized that identical particles like photons could occupy the same energy state, effectively "grouping" them in these states.
This led to a lower probability of high-energy states, resolving the "ultraviolet catastrophe" issue.
Satyendra Nath Bose – Best known for?
Satyendra Nath Bose appeared on the physics scene like a comet.
The year was 1924.
Physics was in the middle of the biggest upheaval in its history.
The old foundations had crumbled in the face of new data.
The picture of a new ‘quantum theory’ was emerging.
But it was a fractured, disjointed picture with major pieces missing.
The search was on among physicists to find the pieces and complete the jigsaw.
In the best universities of Europe, new ideas were being proposed, debated, and discarded every week.
Then a lecturer of physics from Dhaka University — located then in the backwater of backwaters — appeared out of nowhere with a major missing piece of the puzzle.
The lecturer, Satyendra Nath Bose, had discovered the correct set of equations to use to work out the behaviour of collections of photons (particles of light).
As physics work goes, Bose’s was as fundamental as it got.
The physicist and writer Abraham Pais listed it as one of the six foundational papers of quantum theory.
Even so, a paper from an unknown Indian scientist was initially rejected by a journal.
Bose then mailed the paper to his favourite physicist, Albert Einstein, hoping to secure the giant’s support.
Einstein loved the paper, translated it to German, and sent it to a journal himself.
This year marks 100 years of Bose’s discovery.
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