Have you ever been curious as to how light works? Why objects are the color they
are? What if they weren’t really the colors we believed them to be? How would you feel knowing there were whole spectrum’s of light completely invisible to us? Well there are and I’ll explain how we know and why it matters. Color and light affect literally everyone, color helps artists evoke emotions, doctors detect cancer, politicians pull votes, clothing labels target their audiences, and so
much more. For starters we’ll discuss how light behaves and how light allows us to see. Light travels outward in all directions at its source this is called rectilinear propagation of light. We are able to see the world around us because light bounces from objects and is reflected towards our eyes. This redirected light appear as a much smaller up-side down reflected image that is then refocused and made sense in the brain. Light passing through different mediums with different densities will change the speed at which the light travels. This change in speed will refract or bend the light, changing its original coarse. This is only a brief observation as to how light behaves, if we tried to break down exactly how light works, we would be reading an awfully large science book diving deep into quantum physics. [https://www.youtube.com/watch?v=yXaFC2Hko_E]
Quantum physics aside, its obvious light is a very broad subject to tackle. So to keep things narrow, why are objects the color they appear? In ‘The universe explained’ by Heather Couper and Nigel Henbest briefly cover why the sky is blue. A British physicist by the name of Lord Rayleigh was the first person to piece this together. He realized that gasses within our atmosphere were the reason our earthly sky appears blue. When light passes through oxygen and nitrogen molecules, with every pass the light is slightly bent and redirected. These gasses are better at deflecting shorter wave lengths of blue light rather than the longer red wavelengths. We call this effect “Rayleigh scattering”.
Sunlight gets scattered so much by the molecules in our atmosphere, blue light spreads in all directions and is redirected towards our eyes . Light within the visible spectrum appears white until separated by a prism or absorbed by an object, when light is absorbed by an object for example, a green apple, all colors of the white light is absorbed by the apple and green light is reflected, giving the apple its green color. This is the very same concept as to how our sky is blue. Oxygen and nitrogen molecules absorb white light and deflect the remaining blue light in the visible spectrum [11-12]. The human eye is able to see color because of three light receptive cones within the retina that absorb light and translate that information into color. These cones process red, green, blue and all shade variants of these three colors.
Up until now we’ve only discussed visible light and some of its properties, so the next question is, how much light are we not seeing and how do they behave? Well for starters, Radio waves, Microwaves, Infrared, Ultraviolet, X-ray, and Gamma rays are a few (that we know of). The electromagnetic spectrum is the scientific name for the entirety of all light, and our visible spectrum is just a sliver of light in the electromagnetic spectrum. Radio waves are a kind of electromagnetic radiation wave, their wavelengths are longer than that of infrared wavelength. Radio waves cover a very broad frequency within the spectrum, which allows this wavelength to strangely enough carry programmable information from one point to another.
Microwaves are typically used for transmitting information in radar technology, but are most obviously known to be used in microwave ovens, their wavelengths are rough the size of a pencil. Infrared wavelengths are just past the reddest wavelengths of our visible spectrum with a slightly shorter frequency, this spectrum of light although invisible to us radiates a sort of “heat light” that most snakes and reptiles can perceive, So in essence, heat vision. Then there’s ultraviolet light, this is on the opposite end of the visible spectrum bluest light and is also invisible to the human eye. UV rays are highly energetic radiation wave produced by the sun and are the reason we become sun burnt. Most species of birds and insects are able to see this spectrum of light because flowers are highly reflective of UV Rays. This makes the flowers presence more apparent to birds and insects to feed or pollinate from.
X-rays are a very useful wavelength, much shorter in frequency than the other wavelengths we’ve covered. These wavelengths are thousands times smaller and because of their size they are able to penetrate through objects normal light cannot. Similar to how light can easily pass through water or glass, there are materials X-rays are able to pass through without resistance. We use X-rays to our advantage to see through human tissue and observe underlying medical issues such as broken bones. Then we have gamma rays the most energetic and dangerous wavelength within the spectrum. . [Chris Woodford. https://www.explainthatstuff.com/electromagnetic-spectrum.html#page top]
Gamma rays are a form of intense radiation that are extremely dangerous to come into contact with. Gamma rays are the most difficult to detect of all wavelength because of their size. Measuring to about the size of an atoms nuclei, these wavelength are detected using specialized rockets to carry gamma ray sensors high above the earth atmosphere. We use many different kinds of light outside of our visible spectrum to benefit the greater good of humanity. Gamma ray are used in highly concentrated bursts to destroy cancer cells and we use polarized light to detect these cancers cells that would other wise be invisible to the human eye. Imagine if we could see these spectrum of lights completely out of sight and out of mind. Imagine looking up into the sky and seeing your favorite TV show surf through the radio waves above your head ( while this sounds great in theory its closer to science fiction) With more research and new technologies being built to help us see into these invisible spectrums, these efforts will help broaden the human senses and our understanding of how the world works.
1. The Innovation Team RMIT University. “How does light work, and how do we see
it?”. [https://www.youtube.com/watch?v=yXaFC2Hko_E] published on Aug 12, 2014.
2. Heather Couper and Nigel Henbest. “The universe explained: A cosmic Q and A”.
Firefly Books. August 31, 2018
3. April 4, 2012. https://www.sciencelearn.org.nz/resources/47-colours-of-light