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 DIFFERENCE This 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 EQUATION Derivation of the wave equation

WAVE PROPERTIES- PART 1 Reflection Refraction Diffraction

REFLECTION The 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. php

REFRACTION Definition ?? 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 - 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 SuperpositionHuygens’ 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