A simple question I hope, but does radar penetrate glass?
You know those radar transmitters on top of ships, when they are docked and you look though the window from an opposite building 20 meters away, am I being bombarded by radar signals?
How about when you stand on the bridge chatting away with the captain, are we being bombarded with radar signals standing right below the transmitter on the roof?
The radar detector mounted on the inside of the windshield in my truck responds to K, Ka, and X band signals.
yes. radio waves penetrate non conductive materials although there is some reflection at the surface and some loss. Conductive materials largely reflect radio waves although there is some penetration.
Not so much. The radar emission is fairly directional, so that people on the ship itself aren’t really getting much of a dose. There is some spread due to diffraction and other effects, but the majority of the radar energy is directed in a narrow beam in order to maximize range.
All hands, now here this. Do not rotate, radiate or otherwise energize. Men working aloft. That is all.
You’ve already got your answer, so this is redundant, but according to Ben Rich’s book, Skunk Works, one of the biggest challenges in achieving low radar returns on the stealth fighter was dealing with the radar signature of the pilot’s helmet inside the glass cockpit.
~fig
Yes of course, it is obvius now if I think about radar as with light, both being electromagnetic radiation.
But to follow up on the answer that the radar is directional: what if I am on top of the ship roof doing some repairs next to the radar when it is on, how harmful would that be?
It would be similar to being in a really powerful microwave oven I guess.
We use a radar at work which operates in the X-band at about 10 GHz and with an average power of 10 kW. We are not allowed to operate it within 50m of a person, vehicle, or building.
Maybe not quite so obvious. Isn’t UV light stopped by some kinds of glass?
Sailboat
“Ordinary glass is partially transparent to UVA but is opaque to shorter wavelengths while Silica or quartz glass, depending on quality, can be transparent even to vacuum UV wavelengths. Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm”
according to the wikipage on uv-light. Why this is so I do not know.
If it were in the gigahertz range, your eyeballs would explode.
( not quite but here is a cite )
If you look at the photo right at the very top of this site, you’ll see one of the radar domes we maintain. It’s a rotating dish and blows right through that skin. Yours woudn’t have much chance.
There are federal standards for the limits of exposure to EM radiation. Google EM exposure limits.
Even though the antenna is directional there is at least some radiation in all directions. If you are close to the antenna of a high powered emittor you will be in danger of being injured. So the radar will be turned off while you are working. The set will be tagged so no one will turn it on until you are finished. At least that’s the requirement. I, personally, would have a coworker stand by the set with a baseball bat while I was working.
Here’s a site on the Electromagnetic spectrum including a section on atmospheric interations. Scroll down a way to find a graph on the transmissibility of the atmosphere for various wavelengths.
When I was in college, UV erasable eproms were common (these days everyone uses flash chips which are electrically erased). The bulb in our UV eraser broke, and since they were expensive, no one wanted to buy a new bulb. We got the bright idea to stick the eproms next to the window so that the UV from the sun would erase them. Sure, it would take a few days instead of the 30 minutes that the UV eraser could do, but what the heck.
They never erased.
We finally figured out that the window glass was blocking the UV frequencies that the eproms were sensitive to.
I also did some measurements of infrared for a project I was working on many years ago. A 1/2" thick piece of ordinary window glass blocks a significant amount of the infrared light going through it.
Along this same line, a banker in my home town had an invalid son. Doctors recommended that he get as much sunshine as possible. The banker added on a sun room with special glass windows that would pass UV.