Department of Geology and Geophysics
Assignment on GEX 351
Course title : Exploration Geophysics
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Question
List and Explain conditions or fact which could lead to dominance of electromagnetic propagation of diffusion
Assignment on GEX 351 Solutions
We listed 7 Factors please do rearrange it and change some words so that copy work won’t be noticed
Electromagnetic waves can either travel as waves (propagation) or spread out and lose energy (diffusion) depending on certain conditions. Some factors affect whether the wave will move far or weaken quickly. Below are the key conditions that determine if electromagnetic waves will propagate or diffuse.
1. Frequency of the Electromagnetic Wave
The frequency of an electromagnetic wave means how fast it vibrates. This plays a big role in whether the wave will travel far or spread out and disappear.
• High-frequency waves (like radio waves) travel far because they have more energy to move through the ground.
• Low-frequency waves (like those used in geophysics) do not travel far. Instead, they spread out and disappear quickly, causing diffusion.
For example, radio waves from a broadcast station travel over long distances, while the waves used in underground surveys do not go very far.
2. Electrical Conductivity of the Ground
Electrical conductivity means how well a material allows electricity to pass through it. The type of ground where electromagnetic waves pass through affects whether they will propagate or diffuse.
• If the ground conducts electricity well (like wet soil, salty water, or metal-rich rocks), the waves will lose energy fast and spread out, leading to diffusion.
• If the ground does not conduct electricity well (like dry sand or solid rock), the waves will travel further and propagate.
For example, in areas with salty water or wet clay, electromagnetic waves do not move far because they are quickly absorbed.
3. Magnetic Properties of the Ground
Some rocks contain magnetic materials, which affect electromagnetic waves.
• If the ground has a lot of magnetic materials (like iron-rich rocks), the waves will not travel far and will scatter or disappear, causing diffusion.
• If the ground does not have much magnetic material, the waves will move further, leading to propagation.
For example, electromagnetic waves travel better in dry sand than in iron-rich rocks because the sand does not affect the waves much.
4. Water Content in the Ground
Water plays a big role in how electromagnetic waves behave.
• If the ground is wet or contains a lot of water, the waves will spread out and lose energy, leading to diffusion.
• If the ground is dry, the waves will move more easily and travel farther.
This is why electromagnetic waves do not travel well in swamps or oceans but move better in deserts or dry land.
5. Depth of the Waves
How deep the waves go also affects whether they will propagate or diffuse.
• If the waves are shallow (close to the surface), they can move easily and travel far.
• If the waves go deep underground, they may lose energy and spread out, leading to diffusion.
For example, electromagnetic waves used in ground surveys work best at shallow depths because the deeper they go, the more they weaken.
6. Boundaries Between Different Materials
When electromagnetic waves move from one type of material to another (for example, from air to rock or from dry soil to wet soil), some of the energy is lost.
• If the difference between the two materials is large, the waves lose energy and spread out (diffusion).
• If the difference is small, the waves continue moving (propagation).
For example, when waves move from dry soil to wet soil, some of the energy is lost, making diffusion more likely.
7. Strength of the Electromagnetic Source
The strength of the source that produces the waves also matters.
• If the source is strong (like a powerful radio station), the waves can travel far and propagate.
• If the source is weak (like natural signals from the earth), the waves spread out and lose strength, leading to diffusion.
For example, strong signals from a transmitter can travel long distances, but weak natural signals disappear quickly.
Whether electromagnetic waves will travel far (propagate) or spread out and disappear (diffuse) depends on the type of ground, the amount of water, the strength of the waves, and the depth. In places with wet soil, salty water, or metal-rich rocks, waves tend to diffuse. But in dry areas with little interference, waves can travel far and propagate. Understanding these factors is important in geophysics because it helps scientists know how to study underground structures and find useful materials.