# A question about how light hits a surface

my question is about how photons travel from a light source and hit an object.

When you look at an object being hit by light the whole surface becomes brighter.

What i'm trying to understand is why the entire surface lights up.

When the photons leave the light source they scatter out to hit objects, this makes me logicically imaging that a surface will light up based on where those light packets hit.

And not all parts of a surface will light up because the surface area of the light source is too small to match up with each corresponding part of a surface.

Here is a quick text example of what im saying.

LightSource = *

Photons = / or | or \

Surface = _

Expected bright surfaces = %

              *
/ | \
_________
%  %  %


So because the light source's surface area was only big enough able to put out 3 streams of light i expect there to be areas not being hit by light.

So what i want someone to explain to me is why in real life, the entire surface lights up.

Sorry for such a stupid question, i usually keep these kinds of questions to myself but i decided to reach out.

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## 1 Answer

The light from most sources spreads out in all directions so there is a straight line from any point on the surface to the source and a photon heading out from the source in that direction would hit that point.

If you have a source which only emits light in one direction, like a laser, then only a small part of the surface is illuminated and you only see a spot of light

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This is probably the best answer i'm going to get so ill let it go here. –  Necro Feb 25 '13 at 7:42
@Necro - is there something more you need explaining ? –  Martin Beckett Feb 25 '13 at 13:52