Planck’s Quantum Theory:
Background: The Problem with Classical Physics
In the late 19th century, physicists were trying to
understand black body radiation—the way objects emit
thermal radiation. According to classical physics, energy
was thought to be emitted or absorbed continuously.
But this classical idea failed to explain one major
phenomenon:
Ultraviolet Catastrophe
● Classical theory (Rayleigh-Jeans law) predicted that a
black body should emit infinite energy at short
wavelengths (ultraviolet region), which contradicted
experimental results.
● This paradox was known as the ultraviolet
catastrophe.
To solve this, Max Planck introduced a revolutionary idea
in 1900—that energy is not continuous, but quantized.
, Planck's Assumptions and Postulates;
Energy is Quantized
● Matter emits or absorbs energy only in discrete
packets called quanta.
● These packets of energy are the smallest indivisible
units in which energy can exist.
Energy of a Quantum is Proportional to Frequency
● The energy (E) of each quantum is directly
proportional to the frequency (ν) of the emitted or
absorbed radiation:
Background: The Problem with Classical Physics
In the late 19th century, physicists were trying to
understand black body radiation—the way objects emit
thermal radiation. According to classical physics, energy
was thought to be emitted or absorbed continuously.
But this classical idea failed to explain one major
phenomenon:
Ultraviolet Catastrophe
● Classical theory (Rayleigh-Jeans law) predicted that a
black body should emit infinite energy at short
wavelengths (ultraviolet region), which contradicted
experimental results.
● This paradox was known as the ultraviolet
catastrophe.
To solve this, Max Planck introduced a revolutionary idea
in 1900—that energy is not continuous, but quantized.
, Planck's Assumptions and Postulates;
Energy is Quantized
● Matter emits or absorbs energy only in discrete
packets called quanta.
● These packets of energy are the smallest indivisible
units in which energy can exist.
Energy of a Quantum is Proportional to Frequency
● The energy (E) of each quantum is directly
proportional to the frequency (ν) of the emitted or
absorbed radiation:
