As in the case of an object being viewed on the back wall of a camera obscurea
In: Physics
What you see is essentially a negative.
At first, you have white light – all wavelengths are present.
When light hits an object, some wavelengths are removed.
What you see are the reflected wavelengths, which are left after absorption.
In this case, information is added by removal of specific wavelengths.
I.e. a green car will absorb all wavelengths except green*
*Slightly simplified as our eyes/brain will i interpret some mixtures of wavelengths identically to otherw
You can see because light hits an object’s surface and it either bounces back towards your eye(scattering) or, for transparent objects, it is “bent” (refraction) by the object without being absorbed so much, in which case your brain recognizes the “bent” light as something transparent in between.
A camera obscura is basically a box with a small hole through which light passes. Light from the Sun or the environment (e.g. candle, lamp) reaches the object (because most light sources diffuse light in all directions), bounces back in different directions (scattering) and finally reaches the hole (again, because that light goes in different directions, including the hole). You can then see because light hits the hole and from there hits a screen . At this point the image is upside down simply because of the hole: light rays hitting the top of the hole go straight towards the bottom of the screen, and viceversa. You can then reverse the image using a mirror.
If you wonder how it’s possible to “capture” what you see in a photo, the answer is: after entering in the camera, light hits a special “screen” which, in case of analog cameras, is made of a special material that reacts to light by changing the way it’s arranged internally, and in digital cameras is not a “screen” at all but something made of pixels, each of which generates electric current when hit by light.
Light changes in different ways when it bounces off objects different objects. This greatly depends on what kind of light and what kind of object we’re working with. Looking at the changes (before and after) gives us some information about the object.
Sometimes we don’t even care about the changes. For example, Radar scanners simply look at the time it takes for light to travel to and from an object. This tells us information about how far something is.
In the most general sense, light can be a messenger. If you want to send the most basic information like ON or OFF, a pulse of light is the quickest way to do that in this universe. That’s how fiber optic cables work.
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