# Do metals block all frequencies?

Thread Starter

#### Man10

Joined Jul 31, 2018
90
Will metal block all frequencies of radio waves, or are there some frequencies metals won't block? For example will lower frequencies, penetrate metals better? Is attenuate a more accurate term than block?

Thread Starter

#### Man10

Joined Jul 31, 2018
90

#### Papabravo

Joined Feb 24, 2006
16,103
It depends on what you mean by 'lower'.
The plasma frequency of the respective metal determines is what will penetrate at the upper end of the EM energy.

https://uw.physics.wisc.edu/~himpsel/551/Lectures/Plasmonics.pdf
We need more details on the context of your question. Metals as you know will conduct frequencies from DC to hundreds of Gigahertz(≈405 GHz.). IMHO conducting is not blocking. Their temperature will rise in the presence of IR radiation, so that really can't be considered blocking. They will block visible light which is about three orders of magnitude higher in frequency(≈475 THz). Do you want to go higher still?

Thread Starter

#### Man10

Joined Jul 31, 2018
90
We need more details on the context of your question. Metals as you know will conduct frequencies from DC to hundreds of Gigahertz(≈405 GHz.). IMHO conducting is not blocking. Their temperature will rise in the presence of IR radiation, so that really can't be considered blocking. They will block visible light which is about three orders of magnitude higher in frequency(≈475 THz). Do you want to go higher still?
Will any radio frequency pass through a metal or will metals block all possible radio waves?

#### Papabravo

Joined Feb 24, 2006
16,103
Will any radio frequency pass through a metal or will metals block all possible radio waves?
You're looking for a simple answer, and there just isn't one.. The answer depends on the construction and geometry of the metal object. Let us agree on radio waves including frequencies from 10 kHz. up to 405 GHz. I can construct a metal object that will allow radio waves to pass through it. It is also possible to create a metal shield that will block those same radio waves. The thing you may be interested in is called a Faraday Cage, or Faraday Shield.

https://en.wikipedia.org/wiki/Faraday_cage

#### MrSalts

Joined Apr 2, 2020
279
How thick is the metal.

Solid metal, metal laminates, compacted metal powders, compacted insulated metal powders, (concentration of compacted, insulated metal powders - and particle size)

Type of metal - magnetizable, non-magnetizable, high electrical conductivity, low electrical conductivity.

Define "pass through" (passing around a plate, passing through or out of a sealed box, ...)

How is the signal coupled to the metal? Note that antennas are metal. Is the metal connected to signal ground?

Thread Starter

#### Man10

Joined Jul 31, 2018
90
Very well, I fire a focused beam of radio waves at a metal wall. At what frequency will radio waves pass through the metal wall or does the metal wall block all frequencies?
The metal wall has no holes. The shape of the metal object is a 1 inch thick rectangular plate. I think I have described the shape and construction of the metal object in detail. The wall is made of steel?

Thread Starter

#### Man10

Joined Jul 31, 2018
90
The metal wall is not connected to ground. The metal wall is solid metal and not magnetized.

Thread Starter

#### Man10

Joined Jul 31, 2018
90
The metal wall is made of steel. I accidentally put a question mark in this statement"the metal wall is made of steel?".

#### nsaspook

Joined Aug 27, 2009
8,382
Very well, I fire a focused beam of radio waves at a metal wall. At what frequency will radio waves pass through the metal wall or does the metal wall block all frequencies?
The metal wall has no holes. The shape of the metal object is a 1 inch thick rectangular plate. I think I have described the shape and construction of the metal object in detail. The wall is made of steel?
The will be in the X-ray range.

4MeV X-ray range energy into 26mm gives you about 50% transmission. Convert that energy to frequency gives you about 9.6720e+20 Hz

https://www.springer.com/gp/book/9781441981639

#### Papabravo

Joined Feb 24, 2006
16,103
As the article on the Faraday Cage points out. the metal will attenuate the RF energy, but not eliminate it. In QED it is not uncommon for improbable events to happen all the time.

#### MrSalts

Joined Apr 2, 2020
279
I didn't say, magnetized. I said, magnetizable. Now you need to specify what kind of steel. Carbon steel, stainless steel (which alloy - careful, there are magnetizable and non-magnetizable).

Also, which frequency, and how far from the wall is the focused beam. And how are you focusing it?

if you are talking about 10kHz, the wavelength will be 29,000 meters. A non magnetic alloy, not grounded, 1-inch thick will not do much to stop the "beam" because you'll need a 1/4-wavelength antenna or parabolic antenna will be quite far from the wall and will likely bend around any reasonable width or height steel wall (imagine US-Mexico boarder wall).

if you are talking about 100GHz and a low carbon steel alloy, then the beam can be "focused" quite easily with a reasonable sized antenna and the signal will absorb into the wall quite well.

Thread Starter

#### Man10

Joined Jul 31, 2018
90
I didn't say, magnetized. I said, magnetizable. Now you need to specify what kind of steel. Carbon steel, stainless steel (which alloy - careful, there are magnetizable and non-magnetizable).

Also, which frequency, and how far from the wall is the focused beam. And how are you focusing it?

if you are talking about 10kHz, the wavelength will be 29,000 meters. A non magnetic alloy, not grounded, 1-inch thick will not do much to stop the "beam" because you'll need a 1/4-wavelength antenna or parabolic antenna will be quite far from the wall and will likely bend around any reasonable width or height steel wall (imagine US-Mexico boarder wall).

if you are talking about 100GHz and a low carbon steel alloy, then the beam can be "focused" quite easily with a reasonable sized antenna and the signal will absorb into the wall quite well.
Very well, mild steel, a type of carbon steel. The wall is 10 meters tall. There is a receiver with a gain of 5 decibels on the other side. The power output of the transmitter is 2 watts. Distance from transmitter to receiver is 2 meters. How much energy will the steel wall absorb if I use say 600 Mhz? Will the receiver detect the signal?

#### andrewmm

Joined Feb 25, 2011
1,464
I think the answer to the original question is
a solid sheet of metal will attenuate all EM waves, some better than others.

If you think about lead sheet , used to attenuate Xrays,
You can still take Xrays pictures through Lead, you just need a lot more of them ,

So to answer original question,

No

Thread Starter

#### Man10

Joined Jul 31, 2018
90
So attenuate is a more accurate term than block? Just making sure I understand your response.

#### andrewmm

Joined Feb 25, 2011
1,464
Yep,
block implies 100 % attenuation

terribly english language,,
So sun Block, does not actually block the sun to you skin, it attenuates UV,
But I guess the marketing men did not like UVA - UVB but not UVC attenuation cream as a name.

#### Yaakov

Joined Jan 27, 2019
3,152
Because "block" is not a technical term it has no precise definition. You could call attenuation "blocking" and not be wrong because of this.

On the other hand, if you want to communicate technically, you have to use terms that have agreed upon definitions.

This is a general problem with vernacular language when used in any technical conversation that requires precision.

#### andrewmm

Joined Feb 25, 2011
1,464
Because "block" is not a technical term it has no precise definition. You could call attenuation "blocking" and not be wrong because of this.

On the other hand, if you want to communicate technically, you have to use terms that have agreed upon definitions.

This is a general problem with vernacular language when used in any technical conversation that requires precision.
May be off topic,
BUT what the Heck..

Vernacular gets even more fun across countries.
We were taught in cadets the American , we have cleared the building, not to be the same as the UK we have cleared the building.
i.e. in Uk, it means no enemy in building, in US it means we have gone past building..

could be really embarrassing..

English is such a fantastic language !! I only realised when I moved out of the UK , that the book of English rules is small, but the book of English exclusions if Massive .

#### Yaakov

Joined Jan 27, 2019
3,152
May be off topic,
BUT what the Heck..

Vernacular gets even more fun across countries.
We were taught in cadets the American , we have cleared the building, not to be the same as the UK we have cleared the building.
i.e. in Uk, it means no enemy in building, in US it means we have gone past building..

could be really embarrassing..

English is such a fantastic language !! I only realised when I moved out of the UK , that the book of English rules is small, but the book of English exclusions if Massive .
The effect of context can make things even more muddled. Words are amazingly good at adapting to their usage without even the slightest indication they’ve changed meaning entirely.