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University Quantum Mechanics I

University Quantum Mechanics I · The Free Particle · 5.06

Building a wave packet and evolving it

Attach exp(−i ℏ k² t/(2m)) to each component and transform back: free evolution is diagonal in k and never in x.

Course-map guide · not a complete lesson or simulation

Scope & orientation

What this subsection covers

Attach exp(−i ℏ k² t/(2m)) to each component and transform back: free evolution is diagonal in k and never in x.

A strong response uses φ(k) beside the ψ(x) it builds and states where the model stops being reliable.

Reasoning checklist

Evidence, assumptions and limits

01

Assumptions to state

State the system, observable, approximation, and conditions held fixed before using a model.

02

Evidence to collect

In a tank deep enough for kh >> 1, does a group of gravity waves travel at half the speed of the crests inside it, as ω = √(gk) requires?

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In a tank deep enough for kh >> 1, does a group of gravity waves travel at half the speed of the crests inside it, as ω = √(gk) requires? Useful evidence includes video tracking of one crest and of the group envelope, both speeds with uncertainty, their ratio against 1/2, and the two conditions checked explicitly: kh >> 1 needs water 15-25 cm deep with wavelengths of 5-15 cm (a paddle near 3-5 Hz), while wavelengths must stay well above the 1.7 cm gravity-capillary crossover, since below it surface tension takes over and vg exceeds vₚ instead..

03

Limits to state

This GioPhysics course map is an adaptable learning sequence, not academic credit, accreditation, or a universal university syllabus.

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This GioPhysics course map is an adaptable learning sequence, not academic credit, accreditation, or a universal university syllabus. It is a first dedicated quantum-mechanics course, distinct from University Physics V, which covers quantum mechanics alongside atomic, nuclear and particle physics in twenty units: this course is narrower, slower, and teaches the linear algebra it needs rather than assuming it. Hydrogen appears here as an introduction, with the full radial derivation belonging to a second course. A midterm examination is assumed around week 8. Follow your institution's published scope, notation, laboratory programme, and assessment rules. A result should be checked against units, signs, limiting cases, and the conditions under which its model was derived.

Diagram & examples

Work the claim before choosing an equation

Interactive concept map

Follow the model from claim to evidence.

01 · Physical claimBuilding a wave packet and evolving it

Attach exp(−i ℏ k² t/(2m)) to each component and transform back: free evolution is diagonal in k and never in x. Closed forms exist for only a few φ(k); otherwise the integral is an FFT on a truncated grid.

02 · RepresentationThe subsection's claim

Model, evidence, and boundary

03 · TestPrediction before measurement

When should a model used for Building a wave packet and evolving it be revised?

04 · Evidence & boundaryDecide, then qualify

In a tank deep enough for kh >> 1, does a group of gravity waves travel at half the speed of the crests inside it, as ω = √(gk) requires?

Read the complete note

In a tank deep enough for kh >> 1, does a group of gravity waves travel at half the speed of the crests inside it, as ω = √(gk) requires? Useful evidence includes video tracking of one crest and of the group envelope, both speeds with uncertainty, their ratio against 1/2, and the two conditions checked explicitly: kh >> 1 needs water 15-25 cm deep with wavelengths of 5-15 cm (a paddle near 3-5 Hz), while wavelengths must stay well above the 1.7 cm gravity-capillary crossover, since below it surface tension takes over and vg exceeds vₚ instead..

Interactive diagram for Building a wave packet and evolving it: follow the physical claim through its representation, proposed test, evidence, and model boundary.

modelModel, evidence, and boundary turns the stated idea into a representation that can make a prediction.

Example questions

Try the reasoning before revealing the structure.

Diagram check

When should a model used for Building a wave packet and evolving it be revised?

Quick check

Test the reasoning, not recall

When should a model used for Building a wave packet and evolving it be revised?

Choose an answer to test the model.