During an explosion, the sudden release of energy can produce various effects, including a visible blast wave. The visibility of the blast wave is not due to the air itself but rather the phenomena associated with the explosion. Here are a few factors that contribute to the visibility of an explosion:
Shockwave: An explosion generates a powerful shockwave, which is a rapidly expanding and compressing wave of high-pressure gas and air molecules. As the shockwave travels through the surrounding air, it can compress and heat the air, causing it to emit light. This phenomenon is known as shockwave luminescence or Mach stem radiation. The intense compression and heating of air molecules can briefly ionize them, resulting in the emission of visible light.
Heat and Fire: Explosions often produce intense heat and fire, especially if they involve combustible materials. The heat and flames can cause the surrounding air to heat up and glow, leading to visible light emission. This effect is similar to what happens when you see flames or a bonfire—the air surrounding the fire heats up and emits visible light.
Particulate Matter: Explosions can generate a significant amount of debris, dust, smoke, or other particulate matter, depending on the materials involved. When the explosion occurs, these particles may become suspended in the air. As light interacts with these particles, it scatters and reflects, making the suspended matter visible. This scattering of light by particles can create a visible cloud or smoke associated with the explosion.
It's important to note that the visibility of an explosion can vary depending on factors such as the magnitude of the explosion, the materials involved, the environmental conditions, and the observer's proximity to the event.