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# Seeing and photons

If we see an object because of light from the source hitting the surface of the object make its electrons to excite to higher orbits and coming back to same orbit emitting a photon which strikes our eyes, then according to this, at one INSTANT of TIME, an excited electron can emit only one photon and similarly if the object contained (for example) ten electrons on its surface, only ten photons can come form that object at that instant of time and all those photons will have 3 degree of freedom to move in any direction.IF this is the case, we could not see a complete object at a given instant of time as all the photons emitted from that object woudn’t have striken to our eyes and similarly, if 3 people are watching the same object, at a given instant of time, each person would have seen a part of that object as one electron emits only one photon at that instant of time…. but this is not the case in real world….how is it?

We are not seeing an object not just because of a single of photons or not even just a handful of them.

For example, if we have a 100W bulb emitting light of wavelength 6000 angstrom, the total energy emitted per second is 100 J.

The energy of a single photon is

$h\nu&space;=\frac{hc}{\lambda&space;}=\frac{6.6&space;\times&space;10^{-34}\times&space;3\times&space;10^{8}}{6000\times&space;10^{-10}}=&space;3.3&space;\times&space;10^{-19}&space;J$

Which means that each joule of light energy is caused bu 10^18 photons.

A single photon cannot cause the sensation of vision. Remember, we cannot see in dim light. In order to see there must be a minimum required intensity (the number of photons falling per unit area per second multiplied by the energy of a single photon)

It was found that the emission of only 90 photons was required in order to elicit visual experience. However, only 45 of these actually entered the retina, due to absorption by the optic media. Furthermore, 80% of these did not reach the fovea.

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