Chapter 5: Q79CE (page 193)
Sketch the wave function. Is it smooth?
Short Answer
The diagram for the variation of with is given below.
Chapter 5: Q79CE (page 193)
Sketch the wave function. Is it smooth?
The diagram for the variation of with is given below.
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Get started for freeA 50 electron is trapped between electrostatic walls 200eV high. How far does its wave function extend beyond the walls?
If a particle in a stationary state is bound, the expectation value of its momentum must be 0.
(a). In words, why?
(b) Prove it.
Starting from the general expression(5-31) with in the place of , integrate by parts, then argue that the result is identically 0. Be careful that your argument is somehow based on the particle being bound: a free particle certainly may have a non zero momentum. (Note: Without loss of generality, may be chosen to be real.)
A 2kg block oscillates with an amplitude of 10cm on a spring of force constant 120 N/m .
(a) In which quantum state is the block?
(b) The block has a slight electric charge and drops to a lower energy level by generating a photon. What is the minimum energy decrease possible, and what would be the corresponding fractional change in energy?
Consider a particle bound in a infinite well, where the potential inside is not constant but a linearly varying function. Suppose the particle is in a fairly high energy state, so that its wave function stretches across the entire well; that is isn’t caught in the “low spot”. Decide how ,if at all, its wavelength should vary. Then sketch a plausible wave function.
Simple models are very useful. Consider the twin finite wells shown in the figure, at First with a tiny separation. Then with increasingly distant separations, In all case, the four lowest allowed wave functions are planned on axes proportional to their energies. We see that they pass through the classically forbidden region between the wells, and we also see a trend. When the wells are very close, the four functions and energies are what we might expect of a single finite well, but as they move apart, pairs of functions converge to intermediate energies.
(a) The energies of the second and fourth states decrease. Based on changing wavelength alone, argue that is reasonable.
(b) The energies of the first and third states increase. Why? (Hint: Study bow the behaviour required in the classically forbidden region affects these two relative to the others.)
(c) The distant wells case might represent two distant atoms. If each atom had one electron, what advantage is there in bringing the atoms closer to form a molecule? (Note: Two electrons can have the same wave function.)
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