We don’t see light until it’s reflected off something and depending on what the thing is, it absorbs some wavelengths and not others and that’s how we perceive colours. But why? How come we just don’t see all light all the time (when exposed to it)?
In: Physics
>We don’t see light until it’s reflected off something
Not really. We can see the light of a lightbulb (or the Sun, for that matter, although I don’t recommend it) directly by looking at it.
Basically, it’s due to how we see. Our vision works by perceiving the light that enters our eyes. Therefore, it logically follows that what we can see is limited to what enters our eyes. Most of sunlight doesn’t enter our eyes, so we don’t perceive it.
Sunlight shines down on us, so if we’re, say, looking straight forward at noontime, the light rays from the sun are (in general) passing perpendicularly past our eyes, not entering them. But those light rays strike objects around us and then get bounced in all directions, including toward our eyes, allowing us to perceive those objects.
**ELI5:** Imagine you have a cup with a sensor on the inside bottom that detects water. The cup represents your eye and the sensor represents the receptors in your eye. If you turn on a faucet and hold the cup sideways in the water, pretty much no water enters the cup because the opening is sideways, so the sensor detects no water. This is like all the light that goes past our eyes without being perceived/’seen’ because it doesn’t actually enter our eyes. Now put a spoon under the faucet to splash water everywhere. Some of it will get inside the cup and trigger the sensor. This is the light from objects around us, being reflected into our eyes.
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