Ground Penetrating Radar formula

Click For Summary

Discussion Overview

The discussion centers on the physics of ground penetrating radar (GPR), specifically focusing on the derivation of a formula related to the energy reflected and the significance of the dielectric constant (K) in this context. Participants explore theoretical aspects and intuitive explanations regarding the reflection of energy in GPR applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Jerry seeks a derivation of the formula for energy reflected in GPR and an intuitive explanation of the role of the dielectric constant.
  • One participant provides a link to a resource that may contain relevant information about the reflection coefficient.
  • Another participant discusses the formula, noting that the square root can be placed ahead of the expression, indicating that K1-K2 represents the portion of incident power reflected, while K1+K2 represents total incident power.
  • This participant explains that when a wave travels from free space into another medium, changes in permittivity and conductance occur, affecting the electric field and leading to reflections due to impedance mismatch.
  • Water's high permittivity is mentioned as a factor due to its molecular structure, which influences the reflection characteristics.
  • A later reply questions whether the energy is proportional to the square root of the dielectric constant, indicating a need for clarification on this point.

Areas of Agreement / Disagreement

Participants express various viewpoints on the interpretation of the formula and the role of the dielectric constant, with no consensus reached on the specifics of the energy reflection relationship or the implications of the formula.

Contextual Notes

The discussion includes assumptions about the behavior of electromagnetic waves in different media and the definitions of terms like reflection coefficient and dielectric constant, which may not be fully resolved.

PeterPeter
Messages
23
Reaction score
0
TL;DR
Derivation of reflection coefficient?
I am interested in the physics of ground penetrating radar.
1) Does anyone know where I can find a derivation of the formula in the attached jpg for the energy reflected? K=the dialectic constant.
2) An intuitive explanation of why the dialectic constant is important in determining the energy reflected. Obviously it must have something to do with the motion of the free elections.
Thanks in advance
Jerry

Source of jpg:

Interpreting GPR Data: The Basics Part 1 by Greg Johnston
Ground Penetrating Radar formula for reflection.jpg
 
Physics news on Phys.org
In this formula, notice that the SQRT sign could be placed ahead of the whole expression. Then we can see that K1-K2 is the portion of incident power reflected and K1+K2 is the total incident power, so the formula is trivial and not very enlightening. Reflection Coefficient is specified in terms of the fields (or voltages) rather than the power, so we take a square root.
When a wave is traveling in free space, the electric and magnetic fields have a fixed ratio of 377. When the wave enters another medium, such as moist soil, the main things that happen are that the permittivity and conductance increase. Permittivity is associated with capacitance. This causes the electric field to be weaker than in free space, and the ratio of electric to magnetic fields is altered. This is equivalent to the case of a transmission line where there is a change in characteristic impedance. The wave entering the ground cannot suddenly adjust to the new impedance, and part of it is reflected back.
Water has a very high permittivity which is caused by the asymmetrical shape of the molecule, making it polar.
 
tech99 said:
In this formula, notice that the SQRT sign could be placed ahead of the whole expression. Then we can see that K1-K2 is the portion of incident power reflected and K1+K2 is the total incident power, so the formula is trivial and not very enlightening. Reflection Coefficient is specified in terms of the fields (or voltages) rather than the power, so we take a square root...

Are you saying that the energy is proportional to the SQRT of the dialectic constant, K?
 

Similar threads

Borehole / Ground penetrating radar research opportunities
  • · Replies 4 ·
Replies
4
Views
3K
Graduate Ground state energy of cube-like potential wells
  • · Replies 3 ·
Replies
3
Views
2K
Graduate "The 7 Strangest Coincidences in the Laws of Nature" (S. Hossenfelder)
  • · Replies 62 ·
3
Replies
62
Views
11K
Graduate "Monstrous Higgs and Leech Spacetime"
  • · Replies 0 ·
Replies
0
Views
4K
Dielectric constant in the energy density function
  • · Replies 5 ·
Replies
5
Views
8K
I need help, please, designing a pool sensor for breaking . . .
  • · Replies 2 ·
Replies
2
Views
852
Graduate In light of new evidence, what might be behind the Casimir Effect?
  • · Replies 46 ·
2
Replies
46
Views
5K
Graduate Interpretation of quantum fields and their ground state energies.
  • · Replies 9 ·
Replies
9
Views
5K
A Physical Understanding of Kirchhoff's Laws
  • · Replies 18 ·
Replies
18
Views
4K
Sending drive Pulse in CQED and visualize the state by QuTip
  • · Replies 6 ·
Replies
6
Views
4K