Photons do no interact with each other, therefore there will be no energy loss.

Photons do no interact with each other, therefore there will be no energy loss.

Arpad is correct that photons don't directly interact with each other. However the intensity increases quadratically when the focusing radius decreases. High intensity can cause a range of nonlinear optical effects [http://en.wikipedia.org/wiki/Nonlinear_optics] that can actually decrease power at the current wavelength (especially if material with high optical nonlinearity happens to get into focus).

According to quantum dynamics, photons can collide, but with an extremely low probability. The probability is determined by the scattering cross-section of photon, which is very small.

I found some links for you. You can check them out. there has been continuous discussion about this.

http://en.wikipedia.org/wiki/Two-photon_physics

http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.111.080405

http://physics.aps.org/story/v8/st21

Hope those help you.

   The photons can't not directly interact. The vacuum interaction between photons is far too low under earth conditions. Further, the volume of intersection is far from zero.  So saying that the photons are meeting at a point is not strictly correct.  Scientists have not been able to detect nonlinear interactions between photons in a vacuum. Therefore, all measurable optics in the vacuum are likely to be linear.

      The photons are not really being focussed in a vacuum. I hypothesize that they are being focussed in a small volume of air. The air can interact with the light. Therefore, there may be some interactions between photons via the different components of air.

     The nonlinear interactions of light in the air are likely to have several components. I think the largest nonlinear interaction would come from aerosols. Small solid particles, or droplets of water, would be heated by the air. The changes in phase and the changes in temperature are likely to affect the optics.

    For example, a carbon particle could move through the focus. There would then be a direct interaction between the light and the carbon particle. There could be linear interactions such as scattering, extinction and absorption of the light. However, there would also nonlinear effects. The carbon particle could heat, causing the refraction of the gases in the air could change. The light could be refracted by the fluctuations of index of refraction in these gases. This technically could be thought of as an interaction between photons. The carbon particle and the gases would be intermediate in the interaction, of course.

     Another example: a water droplet could get into the focus. The water droplet would refract and scatter some light all by itself. Technically, these would be single photon interactions between the light and the droplet. However, water has a small absorptive component even at optical frequencies. So the water in the droplet could boil, causing additional refraction. Technically, the interaction caused when the droplet boils would be a multi photon interaction. 

   Precipitation, of course, would greatly interact with the light. If a raindrop were to fall at the point of focus, there would be all sorts of interactions both linear and nonlinear.

    Most atmospheric gases are completely transparent to optical frequencies. However, water and carbon dioxide absorb at infrared frequencies. Your solar mirror may be focussing infrared radiation as well as light. So the solar device could be heating the carbon dioxide and water vapor. Of course, the index of refraction changes with local temperature. So there could be nonlinear interaction between the infrared radiation and the visible radiation. 

     I don't know the properties of your optical device. It may be reflecting UV radiation. Nitrogen has some absorptions at the near UV frequencies. Oxygen has some absorption at wavelengths below 230 nm. So the UV could be interacting with the air.

      Solar radiation is not coherent. So I don't think you have to be concerned with coherent nonlinear interactions. However, there may be coherent interactions if you try focusing a laser beam instead of the sun.

      You probably don't have to concern yourself about any of this since the air does not strongly interact with light. However, it may be helpful for you to calculate the total volume of the focussed beam. 

    A noncoherent source like the sun is best analyzed using geometric optics. The volume where the light is focused then comes from the real image of the non coherent source. So if you are focusing the sun, figure out where the real image of the sun is and how intense the light is in that image. Coherent sources of light are different. If you are focusing a laser, you have to use formulas related to Gaussian beam optics.

    I think that you have a small chance of detecting a non coherent and nonlinear interaction between your focused light and the air. I don't think it is likely that this interaction is significant. However, unexpected things always crop up.

I think if you study quantum mechanic, scattering sections, you would get your answer. there are two kinds of scattering:elastic and inelastic. The cross section would be used for calculating the power/dosage.

Cheers,

Narges

In this context, I don't think you need to worry about the particle nature of light (photons) at all. You can do the calculations using basic ray-optics. There will not be any change in the photon energy, as all the interactions here are linear.

A rough calculation will be as following,

Assuming the absorption & scattering at the collector is negligible, Total Power received =  Light intesity at Earth's surface x area of the collector.

Referring Wikipedia, http://en.wikipedia.org/wiki/Sunlight,

The intensity of sunlight at earth's surface is 1120 W/m2 of which  52 or 55 percent infrared (above 700 nm), 43 or 42 percent visible (400 to 700 nm), and 5 or 3 percent ultraviolet (below 400 nm)."

Note : a significant amount of IR will be absorbed when passed through thick glass.

The law of conservation of energy states that total energy cannot change.

go to : Bohr Correspondence Principle and Multiphoton Nature Raleigh Light Scattering Valeriy E Ogluzdin

[Show abstract] [Hide abstract]

ABSTRACT: The correspondence principle and the condition of supplementation were introduced by N. Bohr for the sub-mission of light phenomena, taking into account the wave nature of electromagnetic radiation on one hand, and its quantum structures on the other. In this paper, correspondence principle combines two models of matter, namely, the classical point of view of environment can be considered as an ensemble no equally-frequencies oscillators, i.e. electrons in the surrounding various atoms (molecules) of the matter and characterized by its own set of frequencies (but not hesitant in the absence of an energy source) and the quantum -environment could be presented as a set (ensemble) two-level systems, a wide range of Bohr fre-quencies. According to the correspondence principle Bohr jump-frequencies of atoms (molecules or nano particles) and natural frequencies oscillations of electrons of the same environment -oscillators are equal to each other. The dispersion characteristics of the environment in the every study range of optical frequencies correspond to the model of the classical harmonic oscillator of Lorenz, capable oscillates with Bohr fre-quency. Using the laws of classical mechanics to describe the environment and its dispersion properties, and the simultaneous presentation of light radiation in the form of a beam interacting with the environment of photons (quanta, corpuscles) helps explain peculiarities of the spectral composition Raleigh light scattered.

Journal of Modern Physics 01/2010; 1:86-89.

There will be change in intensity but no change of energy unless scattering is inelastic.

For Raleigh light scattering energy of scattered photons is changeable. They frequency  (energy) is not equal  to frequency pump (initial) photons.