48. From equations (6-23) and (6-29) obtain the dispersion coefficient for matter waves (in vacuum), then show that probability density (6-35) follows from (6-28).

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**Problem 48:**

From equations (6-23) and (6-29) obtain the dispersion coefficient for matter waves (in vacuum), then show that probability density (6-35) follows from (6-28).
Transcribed Image Text:**Problem 48:** From equations (6-23) and (6-29) obtain the dispersion coefficient for matter waves (in vacuum), then show that probability density (6-35) follows from (6-28).
### Transcription and Explanation for an Educational Website

#### Equations and Definitions from Quantum Mechanics

**Equation (6-35):**

The probability density is given by:
\[
|\Psi(x, t)|^2 = \frac{C^2}{\sqrt{1 + \hbar^2 t^2 / 4m^2 \varepsilon^4}} \exp \left[ -\frac{(x - st)^2}{2 \varepsilon^2 (1 + \hbar^2 t^2 / 4m^2 \varepsilon^4)} \right]
\]

**Equation (6-28):**

Another form of the probability density is expressed as:
\[
|\Psi(x, t)|^2 = \frac{C^2}{\sqrt{1 + D^2 t^2 / 4e^4}} \exp \left[ -\frac{(x - st)^2}{2e^2 (1 + D^2 t^2 / 4e^4)} \right]
\]

**Definitions (from Equations 6-29 and 6-23):**

- \( s = \left. \frac{d\omega(k)}{dk} \right|_{k_0} \)
- \( D = \left. \frac{d^2 \omega(k)}{dk^2} \right|_{k_0} \)
- Matter wave dispersion relation: 
  \[
  \omega(k) = \frac{\hbar k^2}{2m}
  \]

### Explanation

These equations represent the probability density of a quantum particle's position over time, described by a wave packet. Such representations are crucial in understanding wave mechanics within quantum theory.

- **\( \Psi(x, t) \)**: This function represents the wave function of a particle at position \( x \) and time \( t \).
- **\( C \)**: A constant that is related to the normalization of the wave function.
- **\( s \) and \( D \)**: Parameters that derive from the dispersion relation of the wave, which determine the group and phase velocity.
- **\( \varepsilon \) and \( e \)**: Parameters related to the spread or width of the wave packet.
- **\( \hbar \)**: Reduced Planck's constant.
- **\( m \)**: Mass of
Transcribed Image Text:### Transcription and Explanation for an Educational Website #### Equations and Definitions from Quantum Mechanics **Equation (6-35):** The probability density is given by: \[ |\Psi(x, t)|^2 = \frac{C^2}{\sqrt{1 + \hbar^2 t^2 / 4m^2 \varepsilon^4}} \exp \left[ -\frac{(x - st)^2}{2 \varepsilon^2 (1 + \hbar^2 t^2 / 4m^2 \varepsilon^4)} \right] \] **Equation (6-28):** Another form of the probability density is expressed as: \[ |\Psi(x, t)|^2 = \frac{C^2}{\sqrt{1 + D^2 t^2 / 4e^4}} \exp \left[ -\frac{(x - st)^2}{2e^2 (1 + D^2 t^2 / 4e^4)} \right] \] **Definitions (from Equations 6-29 and 6-23):** - \( s = \left. \frac{d\omega(k)}{dk} \right|_{k_0} \) - \( D = \left. \frac{d^2 \omega(k)}{dk^2} \right|_{k_0} \) - Matter wave dispersion relation: \[ \omega(k) = \frac{\hbar k^2}{2m} \] ### Explanation These equations represent the probability density of a quantum particle's position over time, described by a wave packet. Such representations are crucial in understanding wave mechanics within quantum theory. - **\( \Psi(x, t) \)**: This function represents the wave function of a particle at position \( x \) and time \( t \). - **\( C \)**: A constant that is related to the normalization of the wave function. - **\( s \) and \( D \)**: Parameters that derive from the dispersion relation of the wave, which determine the group and phase velocity. - **\( \varepsilon \) and \( e \)**: Parameters related to the spread or width of the wave packet. - **\( \hbar \)**: Reduced Planck's constant. - **\( m \)**: Mass of
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