Chapter 7: Problem 27
Compute \(\quad|\Psi(x, t)|^{2} \quad\) for \(\quad\) the function \(\Psi(x, t)=\psi(x) \sin \omega t,\) where \(\omega\) is a real constant.
Short Answer
Expert verified
The short answer to the problem is:
\[
|\Psi(x, t)|^2 = |\psi(x)|^2 \sin^2 \omega t
\]
Step by step solution
01
Write down the given wave function
We are given the wave function:
\[
\Psi(x, t) = \psi(x) \sin \omega t
\]
02
Find the complex conjugate of the wave function
Since \(\psi(x)\) can be complex and \(\omega\) is a real constant, the complex conjugate of the given wave function is:
\[
\Psi^*(x, t) = \psi^*(x) \sin \omega t
\]
03
Multiply the wave function with its complex conjugate
Now, we find the absolute square of the wave function by multiplying the wave function and its complex conjugate:
\[
|\Psi(x, t)|^2 = \Psi(x, t) \Psi^*(x, t)
\]
Substituting the wave function and its complex conjugate, we get:
\[
|\Psi(x, t)|^2 = (\psi(x) \sin \omega t)(\psi^*(x) \sin \omega t)
\]
04
Simplify the expression
Finally, simplify the expression for the absolute square of the wave function:
\[
|\Psi(x, t)|^2 = \psi(x)\psi^*(x) \sin^2 \omega t = |\psi(x)|^2 \sin^2 \omega t
\]
So, the absolute square of the wave function is given by:
\[
|\Psi(x, t)|^2 = |\psi(x)|^2 \sin^2 \omega t
\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quantum Mechanics
Quantum Mechanics is a fundamental theory in physics that describes nature at the smallest scales, including atomic and subatomic levels. It stands as one of the pillars of modern physics, offering explanations for phenomena that cannot be described by classical physics, such as the behavior of electrons in an atom.
In Quantum Mechanics, physical quantities are often represented by operators acting on wave functions, which are mathematical functions that provide the probability amplitudes for the position and momentum of particles. These wave functions are central to Quantum Mechanics since they hold the information necessary to calculate the probabilities of finding a particle in a particular state or location.
The principles of Quantum Mechanics are not just abstract concepts; they have practical applications in technologies like semiconductors, lasers, and medical imaging, fundamentally shaping our modern world.
In Quantum Mechanics, physical quantities are often represented by operators acting on wave functions, which are mathematical functions that provide the probability amplitudes for the position and momentum of particles. These wave functions are central to Quantum Mechanics since they hold the information necessary to calculate the probabilities of finding a particle in a particular state or location.
The principles of Quantum Mechanics are not just abstract concepts; they have practical applications in technologies like semiconductors, lasers, and medical imaging, fundamentally shaping our modern world.
Complex Conjugate
In mathematics, the complex conjugate of a complex number is found by changing the sign of the imaginary part. For example, if we have a complex number 'z' which is 'a + bi', where 'a' is the real part, 'b' is the imaginary part, and 'i' is the square root of -1, its complex conjugate, denoted as 'z*', is 'a - bi'.
The concept of the complex conjugate is a crucial tool in Quantum Mechanics where wave functions may have complex values. Taking the complex conjugate of a wave function is an essential step when calculating physical quantities like probability densities. It is also important when employing operators that are not real but complex values, which is often the case in Quantum Mechanics.
The concept of the complex conjugate is a crucial tool in Quantum Mechanics where wave functions may have complex values. Taking the complex conjugate of a wave function is an essential step when calculating physical quantities like probability densities. It is also important when employing operators that are not real but complex values, which is often the case in Quantum Mechanics.
Wave Function Analysis
Wave function analysis involves examining the properties of wave functions to understand the physical system they represent. In Quantum Mechanics, the wave function is a complex-valued function of the coordinates and time, and its absolute square gives the probability density.
To analyze a wave function, one might explore its time-dependence, look for symmetries, or determine the probability of finding a particle within a certain region. The analysis generally requires a combination of mathematical techniques, including taking the complex conjugate to compute the probabilities. For a given quantum system, analyzing the wave function is essential to predicting how the system will behave.
To analyze a wave function, one might explore its time-dependence, look for symmetries, or determine the probability of finding a particle within a certain region. The analysis generally requires a combination of mathematical techniques, including taking the complex conjugate to compute the probabilities. For a given quantum system, analyzing the wave function is essential to predicting how the system will behave.
Probability Density in Quantum Systems
Probability density is a concept in Quantum Mechanics that indicates how likely it is to find a particle at a particular location in space. Unlike classical physics, where particles have definite positions and trajectories, Quantum Mechanics describes particles through wave functions that provide probabilities rather than certainties.
The probability density is calculated by taking the absolute square of the wave function, denoted as \(|\text{Ψ}(x, t)|^2\). This value is always a real number, which aligns with it representing a real likelihood of particle presence. In the classroom example, we see that by multiplying the wave function with its complex conjugate and simplifying, we arrive at the probability density of finding a particle in space and time, which is proportional to \(|\text{ψ}(x)|^2\) and modulated by \(\text{sin}^2(\text{ω}t)\), reflecting how the probability varies with time.
The probability density is calculated by taking the absolute square of the wave function, denoted as \(|\text{Ψ}(x, t)|^2\). This value is always a real number, which aligns with it representing a real likelihood of particle presence. In the classroom example, we see that by multiplying the wave function with its complex conjugate and simplifying, we arrive at the probability density of finding a particle in space and time, which is proportional to \(|\text{ψ}(x)|^2\) and modulated by \(\text{sin}^2(\text{ω}t)\), reflecting how the probability varies with time.