- #1
ognik
- 643
- 2
(corrections edited in)
1. Homework Statement
Assume ## \psi(x, 0) = e^{-\lambda |x|} \: for \: -\infty < x < +\infty ##. Calculate ## \phi(k_x) ## and show that the widths of ## \phi, \psi ##, reasonably defined, satisfy ##\Delta x \Delta k_x \approx 1 ##
## \phi(k_x) = \frac{1}{\sqrt{2 \pi}} \int \psi(x) e^{-ik_x x} dx ##
## \phi(k_x) = \frac{1}{\sqrt{2 \pi}} [ \frac{1}{(\lambda - i k_x)} e^{(\lambda - i k_x)x} |^0_{-\infty} -
\frac{1}{(\lambda + i k_x)} e^{-(\lambda + i k_x)x} |_0^{\infty} ] ##
## = \frac{1}{\sqrt{2 \pi}} [\frac{1}{(\lambda - i k_x)} + \frac{1}{(\lambda + i k_x)} ] ##
## = \frac{1}{\sqrt{2 \pi}} \frac{2\lambda}{\lambda^2 + k_x^2} ##
What does the width of ##\phi, \psi## mean here? They are ## \Delta k_x, \Delta x ##?
1. Homework Statement
Assume ## \psi(x, 0) = e^{-\lambda |x|} \: for \: -\infty < x < +\infty ##. Calculate ## \phi(k_x) ## and show that the widths of ## \phi, \psi ##, reasonably defined, satisfy ##\Delta x \Delta k_x \approx 1 ##
Homework Equations
## \phi(k_x) = \frac{1}{\sqrt{2 \pi}} \int \psi(x) e^{-ik_x x} dx ##
The Attempt at a Solution
## \phi(k_x) = \frac{1}{\sqrt{2 \pi}} [ \frac{1}{(\lambda - i k_x)} e^{(\lambda - i k_x)x} |^0_{-\infty} -
\frac{1}{(\lambda + i k_x)} e^{-(\lambda + i k_x)x} |_0^{\infty} ] ##
## = \frac{1}{\sqrt{2 \pi}} [\frac{1}{(\lambda - i k_x)} + \frac{1}{(\lambda + i k_x)} ] ##
## = \frac{1}{\sqrt{2 \pi}} \frac{2\lambda}{\lambda^2 + k_x^2} ##
What does the width of ##\phi, \psi## mean here? They are ## \Delta k_x, \Delta x ##?
Last edited: