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CHAPTER 12-WAVES
WHAT IS A WAVE?
Mechanical waves vs non-mechanical waves?
LONGITUDINAL VS TRANSVERSE
KEY TERMS
DISPLACEMENT
AMPLITUDE
WAVELENGTH
PERIOD
FREQUENCY
PHASE DIFFERENCE
PHASE AND PHASE DIFFERENCEThis is a measure of how “in step” the different waves (or particles) are.
CALCULATING PHASE DIFFERENCE
PHASE DIFFERENCE
If the particles are moving together we say they are “in phase”
If the particles are “out of phase” by a half cycle they are π radians out of phase.
A phase difference of π/2 radians shows they are out of phase by ¼ of a cycle
WAVE EQUATIONDerivation of the wave equation
WAVE PROPERTIES- PART 1
Reflection
Refraction
Diffraction
REFLECTIONThe law of reflection from a plane mirror (any flat surface)?
What is TIR?
When does it occur?
DIFFRACTION
When waves pass through apertures or around obstacles they tend to spread out. This spreading out is called DIFFRACTION.
MAXIMUM DIFFRACTION
Maximum diffraction will occur when the gap or obstacle size is close to the wavelength of the wave.
http://www.acoustics.salford.ac.uk/feschools/waves/diffract3.php
REFRACTIONDefinition ??
What would happen if…
Waves in a ripple tank move from shallow to deeper water?
Light travels from air into glass
HOMEWORK!
Discuss the implications of reflection and diffraction on satellite dish design.
Explain one use of TIR in technology
SNELL’S LAW
SNELL’S LAW
SNELL’S LAW - DEFINITION
It is the ratio of the velocity of the wave in the two media
Or the ratio of the sine of the angle of incidence to the sine of refraction
REMEMBER – because it is a ratio, this means the refractive index is a DIMENSIONLESS QUANTITY
SUPERPOSITION AND INTERFERENCE
Wiki Sim – Huygens’ Principle of Superposition
HUYGENS PRINCIPLE OF SUPERPOSITION
The displacement of any point due to the superposition of wave systems is equal to the sum of the displacements of the individual waves at that point