Question about a derivation of jackson

In summary, Jackson states that the number of photons incident on a 1 square centimeter area in 1 second for a 100W bulb at a distance of 1 meter is approximately 10^15. He also provides a similar quantity for an FM antenna operating at 100W and a frequency of 10^8 Hz. To derive these numbers, one needs to find the intensity of the beams by dividing the power by the surface area of a sphere with a 1 meter radius, and then dividing the total energy by the energy of 1 photon. However, the method for obtaining the intensity is unknown.
  • #1
ptabor
15
0
in the introduction to jackson's classical electrodynamics, he states that the number of photons incident to a 1 square centimeter area in 1 s for a 100W bulb (1 m away) is on the order of 10^15.

also he gives a similar quantity for an FM antenna operating at 100W at a frequency of 10^8 Hz.

what's the derivation for these numbers?

I suspect that you need to find the intensity of the beams, then multiply by the 1 cm square to get the total energy - and then divide by the energy of 1 photon ( given by E = hf ).

what I don't know is how to get the intensity.
 
Physics news on Phys.org
  • #2
The intensity is the power (given) divided by the surface area of a sphere 1 m in radius.
 

What is the derivation of Jackson's equation?

The derivation of Jackson's equation, also known as the Jackson's law, is a mathematical formula that describes the behavior of electric and magnetic fields in an electromagnetic wave. It was originally derived by John David Jackson in his book "Classical Electrodynamics".

What are the key components of Jackson's equation?

The key components of Jackson's equation include the electric and magnetic field vectors, the speed of light, and the charge and current densities. These components are used to calculate the behavior of an electromagnetic wave in a given medium.

What is the significance of Jackson's equation in physics?

Jackson's equation is significant in physics as it provides a fundamental understanding of the behavior of electromagnetic waves. It is used in various fields of science and engineering, such as optics, telecommunications, and quantum mechanics.

Can Jackson's equation be applied to all types of electromagnetic waves?

Yes, Jackson's equation can be applied to all types of electromagnetic waves, including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. It is a universal equation that describes the behavior of electromagnetic waves in any medium.

Are there any limitations to Jackson's equation?

While Jackson's equation is a powerful tool in understanding electromagnetic waves, it does have some limitations. For example, it does not take into account the effects of quantum mechanics and does not accurately describe the behavior of very high-frequency waves. In these cases, more complex equations must be used.

Similar threads

  • Introductory Physics Homework Help
Replies
15
Views
1K
  • STEM Academic Advising
Replies
4
Views
2K
  • Introductory Physics Homework Help
Replies
25
Views
2K
  • Advanced Physics Homework Help
Replies
4
Views
5K
  • Advanced Physics Homework Help
Replies
2
Views
2K
Replies
3
Views
1K
  • Advanced Physics Homework Help
Replies
1
Views
2K
  • Advanced Physics Homework Help
Replies
1
Views
2K
  • Introductory Physics Homework Help
Replies
7
Views
1K
Replies
13
Views
2K
Back
Top