If I were to tell you that what comes into the television antenna is not moving pictures, but mere electromagnetic waves in the microwave range, you might take my words for it. You see nothing entering the dish antenna atop your house – no pictures, no music. But you would scoff at my suggestion that there is no light, no trees , mountains or your spouse visible outside your eyes – in fact they are invisible to anything that has no animal optical mechanism. The sun and stars are black bodies that create and radiate electromagnetic energy , NOT light. Ask any blind lady whose optical mechanism has failed for some reason.
The fact is that unlike you or me, the blind lady cannot create light from the electromagnetic energy that enters her cornea, not that she cannot ‘see’ the light that already exists outside. Take, again, the example of a modern television. What is received in those dishes and sent through cables are not pictures or videos, but electromagnetic waves. Within the television, there is a tuning mechanism that resonates only to the frequencies of the channel you selected. Even the antenna – dish or Yagi – is a broadband tuning mechanism that rejects frequencies below the microwave range that is modulated with the frequencies shown within the oval below. The rest of the thingamajig within the television set – the integrated circuits, and components like resistors and condensers together amplify the weak electromagnetic waves and convert them to electrical waves , delivering them to the three Light Emitting diodes behind the glass screen to convert the entire gamut to what is visible to you. That is a simplistic explanation, but you get the gist.
Over a few billion years, Nature created an even better technology than what goes into your TV, but the principle is the same; invented by it through a long process of evolution. Multiple series of fusion that occurs in the sun creates a massive amount of energy part of which radiates in the form of electro-magnetic waves in a whole spectrum of frequencies (conversely described in wavelengths). Our optical system is tuned in to the relatively narrow spectrum roughly displayed below in VIBJYOR colors. Each frequency within this spectrum generates a different colour within the visual cortex of the brain. The areas within the oval outside this spectrum are barely visible Infrared (left) and ultra violet waves (right) that may not generate visible light, but have direct effects on your body.
It is good to remember that as far as it concerns the universe, there is no difference in the characteristics of the waves of EM energy other than the amplitude and frequency.. Our ears, for example, cannot respond directly to electromagnetic waves; they respond to the variations in pressure in the air outside, and the membranes, together with the tiny bones (called hammer, anvil and stirrup) convert those variations to electromagnetic wavesd just as a microphone does in the outside world. Our two ears, placed on the left and right sides of our head, helps us not only to ‘hear’ better and distinguish the ‘colors’ or pitches of the sound which enables us humans and most domesticated animals to distinguish one person from another by the frequency characteristics of one’s sound. Incidentally , like a loop antenna atop an old passenger plane, the twin ears placed on each side of our head help, albeit not too well, locate the source of the sound. So with our eyes which are placed in such a way that the phase differences between the electromagnetic waves received by the cornea of your eyes are focused on to the retina The difference lies in the way different objects respond, or more strictly, resonate to different frequencies of the visual spectrum of a species. T
It is not within the scope of this blog to go into the details as to how the cones and rods wtihin ehelp to distinguish between colors and create electrical signals that go into the visual cortex the brain. Click here to get an idea as to how different parts of the retina, the receptor of electro-magnetic signals that come in through the cornea-lens combination, makes it possible for the cortex to create light and distinguish among millions of colors using three color recognizing cones – Red, Blue and Green. When all these cones are stimulated, you see bright, white light exactly as it happens in your television screen which uses Red, Blue and Green light emitting diodes .
Animals and insects have visible spectra that are different from ours. Since light and its millions of colours are the machination of one’s optical system, and since those machines are not the same any more than the colour of one’s eye might not the same as that of the next person, you know that you like Red, your dear spouse likes red, but how can you be sure that you both see the same red? The little fleas that are deceived into your electric mosquito traps might be seeing neither the blue light nor the amber light bulbs inside, but something very different before they get electrocuted by the wire mesh.. The mosquito with its much smaller slit and a simple optical system, surely has an optical spectrum (not exactly the same as what is within our red oval above) that shifts towards the X-Ray side of the gamut of EM waves shown above. Each eye of the mosquito has not one, but hundreds of lenses to see the tiniest particles such as the red corpuscles in your blood stream and fish them out..
More on the energy (not ‘light’) radiated by the sun and its effect on our Earth, soon follows.
References
https://webvision.med.utah.edu/book/part-i-foundations/simple-anatomy-of-the-retina/
https://www.britannica.com/science/electromagnetic-spectrum
Vishumenon's Blog 