How thick is a light ray

[theedifier]

With reference to light falling on a camera sensor, if each unit of area on the sensor is the size of the impact area of a single ray (not sure if a single ray can be thought of as an arrow making a hole on impact) ... then into how many units can the sensor be divided ... trying to know the theoretical limit of the mega pixels photo that can be captured using a certain size sensor.

 

I am only a science enthusiast and not a professional.

 

Any kind of explanation for a lay man would be helpful.

 

Thanks in advance.

 

[swansont]

Individual atoms can absorb photons. In principle, your sensor could be that size.

[theedifier]

Is it the electron that is absorbing the photon or the atom as a whole ?

[swansont]

The atom is. We often refer to it as an electron changing its energy level, but really it's the bound state of the electron and nucleus.

[theedifier]

Thanks for your help.

 

Could you please clarify if this idea is correct?

 

Each pixel can be as tiny as an atom,

 

Each atom of a photographic film undergoes a chemical reaction based on the energy absorbed by it and thus gives a specific color

 

Since assessing the energy absorbed by each atom of the sensor plate is not practically possible,

the energy absorbed by a certain area of the plate (or all the atoms in the area) is used to identify the color

which would therefore be the combined/average effect of the color relating to all the atoms in that area

 

This is the reason we can say that the photo taken using a digital camera cannot be an equivalent of the photo taken using film camera.

[Enthalpy]

Back to the title question: "rays" are just as wide as light is... That is, if light was emitted by a galaxy 1 billion light-year away, its light is more than one billion light-year wide.

 

Though, one single pixel of the detector in the telescope may detect this light, and even, the photocurrent can be (and often is) measured as individual electrons.

 

That's why physicists (old Albert in fact) introduced the photon. It says essentially that light can be very widespread but its absorption possibly very concentrated and quick.

[swansont]

 

Thanks for your help.

Could you please clarify if this idea is correct?

Each pixel can be as tiny as an atom,

Each atom of a photographic film undergoes a chemical reaction based on the energy absorbed by it and thus gives a specific color

Since assessing the energy absorbed by each atom of the sensor plate is not practically possible,
the energy absorbed by a certain area of the plate (or all the atoms in the area) is used to identify the color
which would therefore be the combined/average effect of the color relating to all the atoms in that area

This is the reason we can say that the photo taken using a digital camera cannot be an equivalent of the photo taken using film camera.

From a practical aspect, I doubt you could make a pixel that small. Photographic film uses crystals which are much bigger than individual atoms. This shows some ~0.5 - 2 microns in size. Digital sensors are down at least to the 2 micron size, but at that point there are other effects that limit the resolution of an image — you have diffraction effects from your aperture.

[MigL]

Electronic 'noise' is the biggest detriment to using small digital ccd/cmos sensors and small pixel size. There are always stray photons impacting the sensor, even infrared or ultraviolet. That's why the better digital SLRs use aps c or full size sensors, and can image at up to ISO6400 with no noise, while the small 'throw-away' digicams are noisy even at ISO800.

 

Think of the sensor pixels as buckets, and light as drops of rain. If the bucket is very small, its very difficult to tell how hard its raining ( light intensity ) because even a stray drop of water will fill the bucket.

[Enthalpy]

Camera pixels are huge as compared to present-days components because they need to catch much light. I see no production reason preventing to make them much smaller, say 50nm*50nm. Performance would be very bad, but such pixels would be 300*300 atoms big.

 

If the wavelength is absorbed only by dopant atoms, then it's easy to have only ONE absorbing atom per pixel - except that some pixels will have zero dopant atom and some 2 or more.

 

Also, some optics experiments are made using a single atom. Sinc decades, so it's not very exotic now.