Wave Physics PHYS 2023 Tim Freegarde. 2 Continuity conditions various derivations and forms...
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Transcript of Wave Physics PHYS 2023 Tim Freegarde. 2 Continuity conditions various derivations and forms...
Wave PhysicsPHYS 2023
Tim Freegarde
2
Continuity conditions
• various derivations and forms
• typically:
• one condition derived from balance of forces• conservation of
momentum• the two conditions combined• conservation of energy
• reduce to equations of the form
where are combinations of material properties
3
Continuity conditions• for a boundary at between regions A
and B:
• transverse waves on a string:
• electromagnetic waves:
non-normal incidence:
• sound waves:
• thermal waves:
4
Reflection at an interface
combine forward and reflected waves to give
total fields for each region
apply continuity conditions for separate
components
hence derive fractional transmission and
reflection
yx
A B
5
Impedance
• sound waves:
• thermal waves:
• transverse waves on a string:
• electromagnetic waves:
• at interface between two media:
6
Electromagnetic waves at a normal interface
combine forward and reflected waves to give
total fields for each region
apply continuity conditions for separate
components
hence derive fractional transmission and
reflection
yx
A B
• continuity conditions:
• parameters:
77
Newton’s rings
diffuser
beam-splitter
lens
plate
s
r
• apply to sinusoidal waves by taking into account the phase with which components arrive• combine by adding the amplitudes
• contributions may therefore interfere constructively or destructively
www.sciencebuddies.org
8
Phase change upon reflection
• phase change if
• for electromagnetic waves
in non-magnetic media
99
Brewster’s angle
www.paddling.net/sameboat/archives/sameboat496.html
ii
r
r
itan• reflected light fully (s-) polarized