It seems like other electromagnetic waves have some special properties. Microwave can heat the water molecules, infrared is basically “heat waves”. UV have enough energy to damage DNA and harm a living things. X-rays and Gamma radiation can penetrate a lot of material and also damage DNA. But the visible part is just visible, or it have some other properties?
In: Physics
>It seems like other electromagnetic waves have some special properties.
Not realy. There is nothing special to microwaves, uv, x-rays or any other electromagnetic wave. The effects you listed are all just results of the wavelength and thus the energy of the wave as energy correleates with the wave length. All electromagnetic waves heat things when they are reflected. All electromagnetic waves penetrate things that are further apart than their wave length. Thats why you can see through air.
One important thing to remember about this electromagnetic waves are a spectrum of wave length and with that wave length the energy changes.
Those properties are not intrinsic to that type of wave though, not really. They are properties that result because of how EM radiation with that particular wavelength is likely to interact with various types of matter, resulting in either absorption, reflection, or just passing straight through.
It is not true for example that visible light is visible and infrared light is ‘heat waves’. It’s just that infrared refers to the range of wavelengths in which most objects which are radiating heat are radiating their heat. Visible light also carries energy and will heat things up when it is absorbed. Heating water molecules similarly isn’t really a property of microwaves per se, it’s rather that EM radiation with a wavelength in the microwave range happens to be just the right wavelength to cause polar molecules to oscillate back and forth.
To some extent this is the case because there aren’t really different types of EM radiation. There’s one type, that can have a range of wavelengths, and we give different names to ranges of those wavelengths based in part on how that wavelength interacts with matter
You are looking at it the wrong way. Whoever discovered UV light thought of it the same way as light unfit for vision.
Our eyes are fine tuned for this particular light. Why did we evolve to see this light and not some other light? Perhaps animals that saw this light were more successful than others.
We know eyes evolved for underwater creatures first so it had to pass through both air and water. We also know that if visible light passed through any object it wouldn’t be very useful to us. So those contraints already narrow it down to visible light alongside other things.
Also not that we sense (but not see) even more invisible light as heat.
It is nothin special except that we can see it, Why we can see it is because tit is a quite narrow band that make up 42% of the energy of sunlight at ground level [https://sunwindsolar.com/wp-content/uploads/2013/06/SunWind-WEB-Solar-Radiation-Spectrum-V2.png](https://sunwindsolar.com/wp-content/uploads/2013/06/SunWind-WEB-Solar-Radiation-Spectrum-V2.png) The peek prightness of the sun is in the visible part of the spectrum. So if you what to pick a spectrum to se reflected light from the sun that is the optimal specrum.
That infrared are heat waves are misleading. Heat is just transfer of energy in a thermodynamic system. Everything emmit electromagnetic radiation and the frequency spectrum depend on the temperature. This is called thermal radiation. For object to release visible light this way then need to be around 500C (900F) to emit a fain red glow we can see. More visible light is emmited the warmer it get.
Even at temperature of 2000 K (1700C, 3100F) 99% of the energy is released in the infrared part of the spectrum. The sun is at 5772K and at temperature like that visible light start to be around half of the energy. I could not find exact number for outside the atmosphere.
We think of infrared light as heat because the heating effect it has on our body is the only way we can detect it. It is alos where most thermal radiation from object on earth are emitted. If you call it heat waves you should call the visible light from the sun heat waves too. It is emmited for the same reason, the sun is just warmer then most stuff on earth. Visible light heat you up just like inraded light, what is added is you eyes ability to see it.
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All those properties are not really defining of those ranges, they just happen. For example, not all microwaves heat water molecules efficiently, it’s just happen that the wavelength that heat the water molecules the most in in the microwaves range.
For visible light, and interesting one is that glass is transparent for it, while it blocks most of the other types of lights.
We see the wavelengths of light that are not absorbed by water. Which is a requirement for a camera that’s in water (the eyeball) . It’s nothing special – it’s just that some wavelengths of light do not interact with water very much. Like a tuning fork only picks up certain sounds, water likewise only picks certain frequencies
What you are describing is how different regions of the spectrum interact with matter. Microwaves photons excite movement in water molecules, causing them to absorb energy and become heated. Infrared photons absorbed by many materials, which are then heated. UV photons have enough energy to excite bound electrons in atoms and molecules. This can cause weak molecular bonds to break, like when DNA is damaged. X-rays and gamma rays can ionize atoms and molecules, breaking molecular bonds.
Visible light photons can excite electrons within atoms and molecules. This can lead to fluorescence or phosphorescence in the right materials. So, exposing glow in the dark objects to light causes them to glow for a while afterwards. Many lasers are also “pumped” by visible light photons, meaning that before the laser can emit light, a bright visible light shines into the lasing material to excite it. Visible light can also be used for heating in the same way that infrared light is. The only problem using a visible light as a heat source is that it will also be bright.
In spectroscopy, electromagnetic wave ranges are categorized by how they interact with matter. For example infrared radiation, when absorbed, makes molecular vibrations stronger (which results in temperature going up); and the reverse is true – when those vibrations get weaker (matter cooling down), infrared light is emitted.
In this context, visible light is categorized together with UV light (together they are called UV-Vis) and when those rays get absorbed, electrons within atoms and molecules move to higher energy levels.
That being said, light types were established before the underlying mechanisms were known so there are a lot of range overlaps and some divisions aren’t very strict
It’s good at passing through water.
That’s because the first eyes developed in the oceans, so they only adapted to see those wavelengths.
Some insects like bees and some birds have adapted to see UV lights, which can pass through the air, but not the water.
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