Waves

Waves

1. 12.1 The Nature of Waves

   • Two Types of Waves
     • Sound, water, waves on springs and ropes, and seismic waves produces by earthquakes. These are mechanical waves. These are vibrations that travel through a medium.
     • Electromagnetic waves- all travel through a vacuum at the speed of 300,000 kilometres. No medium is needed.
       • e.g. light waves, radio waves and microwaves.
     • Longitudinal Waves
       • The oscillations of a longitudinal wave are parallel to the direction in which the wave transfer energy.
       • Waves at which the vibrations are parallel to the direction of energy transfer.
   • Transverse Waves
     • All electromagnetic waves are transverse waves.
     • The oscillations of a transverse wave are perpendicular to the direction in which the waves transfer.
     • A wave where the vibration is perpendicular to the direction of energy transfer.

2. 12.2 The Properties of Waves

   • Amplitude- the wave is the maximum displacement of a point on the wave from it's undisturbed position.
     • E.g. the height of the wave crest from the middle.
   • The bigger the amplitude of the waves, the more energy the waves carry.
   • Wavelength of the wave is the distance from one wave crest to the next.
   • Frequency- the number of waves passing a fixed point every second.
   • The speed of the waves is the distance travelled by each wave every second through a medium.
   • Calculating the speed of sound in air- Speed=distance/time taken

3. 12.3 Reflection and Refraction

   • Reflection- the change of direction of a light ray or wave at a boundary when the ray or waves stays in the insident.
   • Refraction- The change of direction of a light ray when it passes across a boundary between two transparent substances (including air)
   • Incident Waves- waves travelling towards a barrier or a boundary.
   • Wave change speed and wavelength when they cross a boundary between different substances. Unless the waves meet the boundary at right angles, the change in speed causes a change in direction.

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