**Corrections to ***Physics Demystified, 2nd edition*
On page 8, in the fourth line below the subheader "Rules for Use," you'll see the numeral 20,458,000,000. It should read as 24,580,000,000.
On page 112, when I define *mean life*, I continue on to use quantified discussions in terms of a different specification, known as the *half life*. The mean life of a neutron is the average length of time that neutrons in isolation survive: about 15 minutes. The true half life is the length of time it takes for a large number of neutrons (say a million of them) to decrease to half the original number (say 500,000 of them). The half life is about 10 minutes.
If we start with a large number of neutrons and allow the mean life to pass (about 15 minutes), we'll end up with 1/*e*, not 1/2, as many particles still intact. The symbol *e* represents the exponential constant, an irrational number that's quite close to 2.718281828459. Rounded down to six significant digits, 1/*e* = 0.367879. If we start with 1,000,000 particles and wait for the mean life to pass, we'll end up with 1,000,000 x 0.367879 = 367,879 particles, give or take a few from scenario to scenario.
On page 535, Final Exam Question No. 90 should start out by saying, "Meteor-scatter propagation can occur ..." As it reads now, starting out with "Auroral communication," choices A, B, or C could all in theory be correct! The correct choice with this change would be A, as the answer key specifies.
Last updated on May 21, 2016. |