# Waves

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• Created by: Clare
• Created on: 19-11-12 17:32
• Waves
• Waves transfer energy
• Transverse
• Water
• Particle movement is at right angles to the direction
• Up and down- most common
• Longitudinal
• Sound
• Compressions to pass on energy
• Travels parallel to the direction of the wave
• Interferance
• When 2 or more waves come together
• 2 peaks come together
• Constructive
• Wave doubles in size
• Both waves continue in same direction
• 1 peak and 1 trough come together
• Destructive
• Wave cancels out- no sound
• Both waves continue in same direction
• Reflection
• Waves bounce back off the surface at the same angle. Angle of incidence= angle of reflection
• Ray diagram: mirror, normal line, angle of incidence, angle of reflection, incident and reflected ray
• When waves hit a shiny surface they change direction
• Shiny smooth surfaces give a clear image
• Waves  change direction but stay in straight lines (optical fibres)
• Incident ray IN
• Refraction
• Light and sound travel and different speeds in different mediums
• This is due to different densities
• Air and Glass
• Glass= solid more dense
• Waves slow down and bend TOWARDS the normal line
• Think: busy supermarket (more dense) go TOWARDS mum (normal)
• Doesn't occur at 90 degrees
• Angle of refraction is less than angle of incidence
• After leaving glass block the ray is bent back to it's original direction
• Diffraction
• Bending of a wave around an obstacle, past an object or through a gap
• No properties are changed during diffraction- only DIRECTION
• Travelling through a gap- wave travels straight on then expands outward (semicircle)
• Travelling around a corner- once past corner expands circularly
• Parts of a wave
• Wavelength
• Distance from peak to peak
• Amplitude
• Height from middle line
• Frequency
• Number of waves passing a point in a second
• Measured in Hertz (Hz)
• Frequency= no. of waves/ time in secs
• Peak/ Trough
• Wave speed= frequency x wavelength
• Wave speed- how fast a wave travels through space