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1. If you want another confounding factor think on this. The light intensity at any point in space away from a point light source is zero. A point in space has zero area so no photons can pass through it. And yet an illuminated surface consisting notionally of uncountable points with no spaces between them does intercept photons.

2. Originally Posted by Maris
If you want another confounding factor think on this. The light intensity at any point in space away from a point light source is zero. A point in space has zero area so no photons can pass through it. And yet an illuminated surface consisting notionally of uncountable points with no spaces between them does intercept photons.
It's not a series of points, it's called a plane. Planes have area, points don't. Points are points in space, and have no volume. Planes are a surface that occupies space....

3. Originally Posted by AgX
Like shortening flash-duration at an electronic flashlight. In practice already the delivered electrical energy is huge, though only for an extreme short time. Reducing duration time to infinitively small values would make the spent energy infintively large.
This is not true.

Shortening a flash-duration would not increase the instantaneous power output of the flash, it would stay the same. To attain the same overall light output hitting the subject, you'd have to increase the instantaneous power output of the flash.

4. In out, PM me if you want me to ask my dad anything else...

5. Originally Posted by Prof_Pixel
As the distance approaches zero, the intensity asymptotically approaches infinity. You can never reach zero distance.
Then how does something "approach" zero or infinity? No matter how small something gets, it is always infinitely far away from zero, and now matter how large, it is always infinitely far away from infinity.

6. I think if the light source is a true point source that is a point with no dimension then it's possible to have infinite intensity

7. Originally Posted by RPC
Then how does something "approach" zero or infinity? No matter how small something gets, it is always infinitely far away from zero, and now matter how large, it is always infinitely far away from infinity.
I take it you've never studied calculus? It includes a study of limits (as in the limit when something approaches zero or infinity).

8. Originally Posted by Chan Tran
I think if the light source is a true point source that is a point with no dimension then it's possible to have infinite intensity
that was my point ,hence the doubt about the equation

9. I was going to say maybe the limit was a half-inch. But looking at the kinds of devices that you can setup to take advantage of inverse square law, I could imagine a "grease spot photometer" could be invented to fit within a rangefinder of a camera, and there's no reason this device couldn't be a quarter-inch overall and still be effective.

10. Originally Posted by Prof_Pixel
As the distance approaches zero, the intensity asymptotically approaches infinity. You can never reach zero distance.
Yes.

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