GREPhysics.NET
GR | # Login | Register
   
  GR9677 #17
Problem
GREPhysics.NET Official Solution    Alternate Solutions
This problem is still being typed.
Quantum Mechanics}Probability


The careless error here would be to just directly square the grids. When one remembers the significance of the meaning of the probability P=\int |\langle \psi | \psi \rangle|^2 dV, one finds that one must square the wave function, and not the grids.

The total probability is,


The un-normalized probability from x=2 to x=4 is,


The normalized probability is thus 13/16, as in choice (E).



See below for user comments and alternate solutions! See below for user comments and alternate solutions!
Alternate Solutions
There are no Alternate Solutions for this problem. Be the first to post one!
Comments
mhazelm
2008-09-08 12:05:19
If you are familiar with probability theory, this amounts to computing the probability of event A, where A is the the particle's being between x =2 and x=4. From probability, this is given as

P(A) = # ways A can occur/# total possible outcomes.

Now # ways A can occur: if x is between 2 and 3 (an interval of 1) then Psi takes on the value 2 (so Psi^2 = 4). If x is between 3 and 4 (another interval of 1), then Psi^2 = 9. Thus # ways A can occur = 4+9 = 13.

Now for the total number of possibilities, we just do the same thing, but for all possibilities of x. Our intervals are all 1, so we get

1(1^2) + 1(1^2) +1(2^2) + 1(3^2) + 1(1^2) = 16. Now just use the fact that P(A) = 13/16 and you're done with answer E being correct.
NEC

Post A Comment!
Username:
Password:
Click here to register.
This comment is best classified as a: (mouseover)
 
Mouseover the respective type above for an explanation of each type.

Bare Basic LaTeX Rosetta Stone

LaTeX syntax supported through dollar sign wrappers $, ex., $\alpha^2_0$ produces .
type this... to get...
$\int_0^\infty$
$\partial$
$\Rightarrow$
$\ddot{x},\dot{x}$
$\sqrt{z}$
$\langle my \rangle$
$\left( abacadabra \right)_{me}$
$\vec{E}$
$\frac{a}{b}$
 
The Sidebar Chatbox...
Scroll to see it, or resize your browser to ignore it...