Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

A question about RADARs

  1. Jan 27, 2005 #1
    Hi, I have a question wich should fit in here:

    - How big in size may an object be before it's noticed on a radar screen?

    Could it detect a fly if it's designed to do that, or must the size be in a airplane dimention?

    I hope that someone can think of a good answer to this question :)
  2. jcsd
  3. Jan 27, 2005 #2
    the object must satisfly these two conditions in order to be detected by radar

    1: It must reflect the radar ray..... even the B2 bomber is so large, but it has a coating on its skin to absorb radar ray, therefore radar can't detect it
    2: the object must much larger than the wavelength of the radar ray you used... for a normal aircraft used radar, the wave length is about 3cm...

    a fly don't reflect the radiowave very well, and too small compare with the radar's wavelength
  4. Jan 27, 2005 #3
    Well, it's bit more complicated than that.


    An important element is http://www.argospress.com/Resources/radar/radarcrossectio.htm [Broken]. A square metal can of a few inches could have a RCS of 10m2 while a stealth fighter may have a RCS of a marble.

    Radar absorbing paint may only reduce the RCS, it's not making it dissapear.
    Last edited by a moderator: May 1, 2017
  5. Jan 29, 2005 #4
    thanks guys, a lot of usefull information there ;)
  6. Jan 31, 2005 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Of course, the amount of power transmitted by the radar, and the radar's sensitivity to its echoes, are very important, too.

    - Warren
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook