A quantum of energy refers to the smallest discrete unit of energy that can be emitted or absorbed in the form of electromagnetic radiation. In the context of quantum mechanics, energy is not continuous but rather exists in specific packets called ‘quanta’.
To understand this concept better, consider light. Light can behave like both a wave and a particle. When we talk about the particle aspect of light, we refer to photons. Each photon carries a specific amount of energy that can be calculated using the equation E = hν, where E is the energy of the photon, h is Planck’s constant (approximately 6.626 × 10^-34 Js), and ν (nu) represents the frequency of the light.
This means that energy is quantized, which is a foundational concept in quantum physics. For example, when an electron in an atom absorbs a photon, it gains a specific amount of energy corresponding to the energy of that photon. If the photon has an energy that does not match the energy difference between the electron’s current state and a higher state, the electron will not absorb it. This quantization of energy levels in atoms is what leads to various phenomena, such as the emission of light at specific wavelengths, contributing to the colors we see.