We want to see how the characteristics of the light vary with the distance from the perspective of plants.
We know that light is an electromagnetic wave. So if we have a source that emits light in a homogeneous way (not a realistic thing, but enough to explain the general properties, this means that the source emits the same amount of light in all directions) we would see spherical waves of light. Now the amount of light that comes out of the source is constant.
This means that as that sphere of light increases (note that the photons are on the surface of the sphere) the number of photons per differential of surface decreases.
This happens because the total surface of that sphere keeps increasing, but the number of photons remains constant.
And because it is a surface what is being increased as the sphere increases, we can say that the intensity (amount of photons) decreases proportionally to it.
Then the intensity of the light decreases with the distance squared from the source.
So if your plant has a fixed effective surface area, you know that the amount of light that reaches that area decreases with the distance squared between the plant and the source.
The color variation really is harder to see. Let's observe the light that comes from the Sun.
When the Sun is above us (parallel to the sky above us), the sky is blueish.
When the Sun is perpendicular to the sky above us, the sky is reddish.
This happens for the rayleigh scattering, in which depending on the distances, angles, and materials, some components of light may be filtered.
But we can't really find an exact relation between distance and variation in color due to the complexity of this phenomenon.
In essence, we can say that the frequencies that the plant sees during the day are more blueish (more energetic) while the ones that it sees near the sunrises or the sunset are more reddish (less energetic).
For the cases of indoor grows, where an electrical source is used, the distances are so short (and light travels so fast) that changes in the color of the light are negligible.
If you want to learn more, you can read:
https://brainly.com/question/13667027
