Light possesses the unique nature of being both a wave and a particle. This property, known as duality, allows us to explain light’s behavior from two different perspectives. In this post, we’ll delve into the terminologies that are essential for understanding the dual nature of light.

Wave–Particle Duality of Light

Physics  · 

The speed of light in a vacuum can be derived from the fundamental constants of permittivity (\(\epsilon_0\)) and permeability (\(\mu_0\)), illustrating light’s wave-like properties:

\[c = \frac{1}{\sqrt{\epsilon_0\mu_0}}\]

Conversely, when considering light as a collection of particles known as photons, its speed can also be represented as the ratio of a photon’s energy to its momentum:

\[c = \frac{E_{photon}}{p_{photon}} = \nu\lambda = \frac{\omega}{k}\]

Here, the energy (\(E_{photon}\)) and momentum (\(p_{photon}\)) of a photon are given by:

\(E_{photon} = \hbar\omega\) \(p_{photon} = \hbar k\)

where \(\omega\) is the angular frequency and \(k\) is the wave vector, linked to the frequency (\(\nu\)) and wavelength (\(\lambda\)) of light by:

\(\omega = 2\pi\nu\) \(k = \frac{2\pi}{\lambda}\)

In these expressions, \(\hbar\) denotes the reduced Planck’s constant, a fundamental quantity in quantum mechanics that relates the energy of a photon to its frequency.