| Share


barn, abbr. b, in physics, unit of nuclear cross section, i.e., the effective target presented by a nucleus for collisions leading to nuclear reactions; it is equal to 10 - 24 square centimeters. The barn is approximately the size of the geometric cross section of an atomic nucleus; the term was coined because an effective cross section that large would present a target "as big as a barn," i.e., an easy target for nuclear bombardment. In practice, effective cross sections of nuclei for many reactions are measured in millibarns (10 - 3 barn) because, for most interactions, only a small fraction of collisions cause reactions.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.

More on barn from Infoplease:

  • Barnes: meaning and definitions - Barnes: Definition and Pronunciation
  • Barnabe Barnes - Barnes, Barnabe Barnes, Barnabe, 1569?–1609, English poet. His major work is Parthenophil and ...
  • Albert Barnes - Barnes, Albert Barnes, Albert, 1798–1870, American Presbyterian clergyman, b. Rome, N.Y. From ...
  • William Barnes - Barnes, William Barnes, William, 1801–86, English poet and philologist. After a career as a ...
  • Djuna Barnes - Barnes, Djuna Barnes, Djuna , 1892–1982, American author, b. Cornwall, N.Y. She is best known ...

See more Encyclopedia articles on: Physics

24 X 7

Private Tutor

Click Here for Details
24 x 7 Tutor Availability
Unlimited Online Tutoring
1-on-1 Tutoring