Describing a photon as "pure energy" is a simplified way of expressing its nature and properties. In physics, photons are considered fundamental particles of light and electromagnetic radiation. They are the basic units or quanta of electromagnetic energy.
Here's a more detailed explanation: According to quantum theory, electromagnetic radiation, including light, can be understood as consisting of tiny discrete packets or quanta called photons. Photons are massless particles that travel at the speed of light and carry a specific amount of energy. The energy of a photon is directly proportional to its frequency or inversely proportional to its wavelength, as described by the equation E = hf, where E is the energy, h is Planck's constant, and f is the frequency.
Photons have wave-particle duality, meaning they exhibit both wave-like and particle-like behaviors. When they interact with matter, they can behave as particles, transferring their energy and momentum to atoms or electrons. At the same time, they can also exhibit wave-like characteristics, such as interference and diffraction patterns.
So, when we say a photon is "pure energy," it means that it carries energy without having any mass associated with it. It is the energy carrier of the electromagnetic force. However, it's important to note that photons are not energy in the sense of a substance or a material form. They are fundamental particles that carry energy and interact with matter and other particles.