Why can you see through glass but not through wood?

Imagine a world where we could see through everything. A walk in the park would certainly be less scenic, wouldn't it? Luckily, the way visible light interacts with different materials saves us from that oddity and enriches our visual experiences. Visible light is the portion of the electromagnetic spectrum that our eyes are equipped to detect. This sliver of the spectrum ranges from about 400 nanometers (violet) to 700 nanometers (red).

When visible light rays hit an object, several interactions can take place. They can be transmitted, akin to a car driving through an empty street; reflected, much like a basketball bouncing off the court; or absorbed, similar to a sponge soaking up water. These interactions are influenced by the atomic and molecular structure of the material the light is encountering. For instance, glass transmits light almost like a clear path due to its orderly structure, while materials like wood block and absorb light due to their complex, irregular composition.

Have you ever wondered why we can't seem to play hide and seek behind a window? It's because of something called transparent materials. These are the Houdinis of the material world, letting light pass through them as if they aren't even there. Transparent materials have a special knack for transmitting visible light with minimal absorption and scattering. It's like a gentle whisper that passes through without causing much disturbance.

One of the best examples of a transparent material is glass. It is composed of silicon dioxide molecules that have a consistent, somewhat random arrangement. The glass doesn't bother the light waves much, so they continue on their way and allow us to peek through windows or wear spectacles without obscuring our vision.

On the flip side of transparency, we have opaque materials. These are the introverts of the material spectrum, stopping light from entering their personal space. Unlike transparent materials, opaque objects absorb or scatter all the light. Think of a curtain that blocks out sunlight, allowing you to sleep in darkness.

Wood is an example that resembles a maze for light waves; with its cellulose fibers and other organic compounds, it causes light to bounce around and be absorbed, preventing any possibility of the light traveling straight through. This inherent obstacle course within the wood is the reason we can't see through it. It's not just being stubborn; it's how nature designed it.

So what’s the bigger picture behind all this talk of transparency and opacity? It's a phenomenon called electromagnetic radiation, a form of energy that is all around us and takes on many forms, including visible light. Electromagnetic radiation waves are the social butterflies of the energy world, capable of traveling through space and matter.

Aside from the visible light we've been talking about, electromagnetic radiation includes radio waves that carry our music, microwaves that heat our leftovers, X-rays that peek inside our bodies, and much more. Each type interacts with materials in distinct ways depending on their wavelength and the material’s properties, which is a fascinating demonstration of how diverse and intricate the universe really is.