We often compare light and sound because they correspond to two senses that inform us about our surroundings remotely. But from a physicist’s perspective, they are very different. Light can be described by weightless little particles moving at very high speed, called photons, while sound is what we perceive from small variations in the density of the air around us. When thunder breaks, the lightning emits photons which travel almost freely towards us, at a speed that would make them reach the Moon in about a second. Lightning also disturbs the surrounding air molecules, and this is what produces sound: the disturbance in the air propagates from molecule to molecule until it reaches our ears. This makes it much slower than photons. Actually, while sound needs a medium like air or water to propagate, photons can travel in empty space, which is how the Sun’s light reaches us.
Did you know?
- Sound travels at about 330 metres per second while light travels at 2,99,792.458 km per second.
- Because light travels faster than sound you see lightning before you hear the thunder.
- Insects such as bees and spiders are capable of viewing ultraviolet light, while reptiles like snakes can view infrared lights.
- Human ears are only capable of hearing frequencies of about 20 kilohertz, while the species that is known to have the highest capability of hearing, the Greater Wax Moth, can hear frequencies of around 300 kHz.
- When travelling through water, sound moves four times faster than when it travels through air.
Picture Credit : Google
