How could you test that gamma rays spread out in different directions?

An individual gamma ray (photon) doesn't spread out (excepting double-slit type experiments), but it is straight forward to demonstrate that the angular distributions of photons from incandescent lamps and gammas from radioactive sources are isotropic using detectors. But put a supercooled Cobalt-60 radioactive source in a strong magnet and you could have won a Nobel Prize. See

http://physics.nist.gov/GenInt/Parity/expt.html [Broken]

Bob S

 

Well, what you would need would be a gamma ray source and a detector.

One simple experiment (assuming that your source strength is low enough not to pose any significant danger from radiation exposure) would be to place your source on a sheet of film for a period of time long enough to expose the film, then develop it (or, of course you could just use radiochromic film). If the film is properly calibrated, you will end up with a map proportional to the radiation intensity through a plane, thus demonstrating that the gamma rays are spreading out in all directions. You could carry it further and show that the intensity of the radiation falls off in a 1/r^2 for distances much greater than the dimensions of your source.