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Instructor’s informal sessions:

• Tuesday 3:30-4:20, WAG 420
• Friday 4-5pm, RLM4.102.

Lecture 35

Qualitative description of waves

· Oscillatory source, medium (matter stays), wave pattern travels

· Transportation of energy

· Transverse waves and longitudinal waves

Transverse traveling waves

· Fixted t: Sinusoidal pattern in x, l, k=2p/l

· Fixed x: SHM in y, T, w=2p/T

· Fixed q: v=w/k=l/T.

Wave speed: v=(F/M/L)^1/2.

· Derivation: DFcp=TDq.

Superposition of 2 waves

· y=2A cos[|q1-q2|/2]cos[|q1+q2|/2]

Beats

· y=2cos[Dwt/2]cos wt

· | DwT_beat/2|=p àf_beat=|f₂-f₁|

Standing waves:

· Antinodes and nodes

· Reflection at a fixed point

· Normal modes on a string segment fixed at both ends

Reminders:

· Read chapters 16 and 17. Begin HW12.

· Remember there is Instructor’s informal session tomorrow.

· Link the update on our syllabus, click here. It is posted also in the main website of this course.

We need your help: After you have completed your reexam03, please email us your opinion:

• Is a good idea for us to continue the reexam scheme in future semesters?
• Any additional suggestions about the reexam scheme and about this course are welcome also.