Why does visible electromagnetic radiation (light) is easily blocked by an object, but radiation of lower frequency like radio or cellphone signals can easily travel through obstacles to a degree?
In: Physics
Oooh I knowww this one. TL/DR below.
First, EM radiation can be considered a quantum wave. By wave, I mean like a string being jiggled up and down and particles sit somewhere on this string. Think of the string passing through a pair of walls. When wiggled bigger than the opening the wave structure breaks down, this is called diffraction. EM radiation is weird because it acts oppositely to this. When the string is waving smaller than the opening it breaks down when traveling through. More on this in a minute..
Secondly, we consider how we can make the string wiggle within a smaller space. This is considered with wavelength. Larger wavelength is associated with low frequency which leads to longer travel due to lack of absorption (stuff that stops the “flow” of the waves). Now, thinking of absorption associated with wavelength and thinking of wiggling the string through the doorway we have to consider what happens when the string breaks down. This is called destructive vs constructive interferences. It happens when the opening (walls gap) is similar, a little bigger, or a little smaller, than the wiggles of the string. When bigger it breaks down (destructive), when smaller or similar size it propagates (constructive intereference = continues to move).
Now, let’s add some pieces together. Larger wiggles travel further in similar or slightly smaller wall gaps. We finally ask, WHY?? The answer comes down to being similar to waves of an ocean. When the waves are BIG they simply flush themselves around small objects and continue on, sometimes they’re big enough to take the items with them, like boats. When they’re small, small objects can absorb them and they break down. And that’s about it.
Above a 5 year old: objects are made of atoms that sit close together. These atoms can only vibrate so much before they require an immense amount of energy to move them any further. The amount of room an atom can vibrate is the wall gap idea. Smaller waves get absorbed between these atoms and as they come in contact with molecules. Larger wavelengths have the energy to push their way through. This is why an object can heat up when put under a lot of sound or how microwaves work.
TL:DR light is made up of small quantum waves (like ocean waves) where radios are considered larger waves. Larger waves can travel further than smaller waves because they can move past themselves and other smaller objects. Small waves get absorbed by smaller object. Light is easily absorbed by small molecules where radio waves are not.
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