# Frequency and penetrating power

1. Jun 30, 2014

### Entanglement

How are penetrating power of a EM wave and its frequency related?

2. Jun 30, 2014

Staff Emeritus
What have you done to find the answer to this? And what part didn't you understand?

3. Jun 30, 2014

### UltrafastPED

Longer wavelengths penetrate further; it is a fundamental property of waves.

4. Jun 30, 2014

### Entanglement

I know that waves of higher frequencies and shorter wavelengths have higher penetration power, I know the fact but I don't know the reason, I'm not even sure whether the fact is right or wrong

Last edited: Jun 30, 2014
5. Jun 30, 2014

### Entanglement

Then why it always said that high frequency waves have high penetrating power just as x rays ??
Can you please explain how EM waves' wavelengths governs its absorption, reflection and penetration ??

6. Jun 30, 2014

### Drakkith

Staff Emeritus
I'm pretty sure high-energy EM radiation doesn't follow this property.

7. Jun 30, 2014

### Delta²

There is the particle-wave duality.

At lower frequencies (say no more than afew Ghz) the EM-wave acts mainly as wave according to Maxwell's equations , interacts mainly with the free electrons of the matter and a well known phenomenon knows as skin effect arises where the EM-wave's electric field and the induced current density exist mainly in a very thin layer near the surface of the conductor. The depth of this thin layer is inversely proportional to the frequency of the EM wave.

At very high frequencies (afew hundred Ghz and further into the Thz realm) the particle nature of the EM-wave becomes predominant and the particles of the EM-wave known as photons interact in general with all the particles of the matter according to the laws of quantum physics. The higher the frequency of the EM wave, the more energy and momentum the photons have , thus the further into the material they can penetrate.