1. Planck's Quantum Hypothesis

Concept Explanation:

Max Planck, a German physicist, proposed the quantum hypothesis to explain blackbody radiation, which classical physics could not adequately describe. Planck suggested that energy is not continuous but rather quantized, meaning it can be emitted or absorbed in discrete amounts called "quanta." The energy (E) of each quantum is proportional to the frequency (ν) of the radiation:

E = hν

Here, h is Planck’s constant, with a value of approximately 6.626 × 10⁻³⁴ joule-seconds.

This idea marked the birth of quantum theory, fundamentally changing our understanding of physics by introducing the concept that energy levels are discrete rather than continuous.

Example Problem:

Calculate the energy of a photon with a frequency of 5 × 10¹⁴ Hz.

Solution:

Using Planck's equation:

E = hν

Substitute the known values:

E = 6.626 × 10⁻³⁴ J·s × 5 × 10¹⁴ Hz
E = 3.313 × 10⁻¹⁹ J