How light enables us to see? Is there any alternative of light?
In: Physics
The light reflects from surfaces at different angles and hits the retina, where a lot of processing happens and the transduced signal is finally sent up to the brain via the optic nerve. The brain takes that neural information and painstakingly (re)constructs the object the light has bounced off. Additionally, the length of the reflected lightwaves with provide information about the color of the object (or at least what that color looks like for us).
We do not really “see” – reflected light hits our eyes, and the brain does the rest based on that information.
Light enables us to see because our eyes are only capable of processing light, there is no alternative for humans. BUT, other animals have echolocation (bats, whales, …) so they can perceive their environment using sound. It’s not exactly the same as “seeing”, as bats also have eyes that see light like ours.
Humans also have science, so we can translate many other things, even sound, into things we can see by using computers to process the data from that other source and light up a screen with light our eyes can see.
Seems like you already understand that the light is reflecting off of the object and hitting your eyes. From there, though, it gets pretty complicated; the eye is the second most complex organ in the body (second only to the brain), and there are over two million working parts that help turn those waves of visible light into information that your brain can use. For the sake of simplicity, let’s just say that the light gets angled towards the back of the eye, where the retina absorbs it with its millions of tiny, sensory cells called rods and cones. These rods and cones turn the light waves into electrical signals, and send these down the optic nerve into the brain. From there, your brain makes sense of all of these signals, and factors in both eyes to give you depth perception as well. It’s a beautifully complex process, especially considering how quickly and effortlessly it all seems to happen.
Humans can only receive visual stimuli through visible light. Some other organisms can use infrared or ultraviolet light (the waves just outside of red and violet light, respectively), but we cannot. Similarly, some organisms like bats can gain spatial information through echolocation, where they bounce sound waves off of objects and back to themselves. We can do this in an extremely rudimentary sense (imagine closing your eyes and shouting to see if there’s a door in front of you), but it won’t tell us nearly as much about our surroundings as visual light would.
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