Topic 4- waves

• Transverse waves-


  Oscillate at right angle to the direction of travel (side to side)
• Longitudinal waves-


  Oscillate parallel to the direction of travel (up and down)
• The Electromagnetic Spectrum-


  Radio waves, Microwaves, Infrared, Visible Light, Ultra-violet, X-ray, Gamma
• Frequency-


  The number of waves that pass a certain point in a second.
• Period, or time for one wave, can be found from 1 over the frequency.
• Wavespeed (m/s)=


  Frequency (hz) x Wavelength (m)
• Wavespeed (m/s)=


  Distance (m)/Time (s)
• Transverse waves: s-waves, side-to-side waves, slow, secondary only pass through solids
• Longitudinal waves: p-waves, push-and-pull, primary will pass through solid, liquid and gas.
• The density of the earth increases the further down you go so the speed of the wave changes, they are refracted.
• Refraction of p-waves in the liquid outer core explains the shadow zone.
• Reflection of s-waves can be used to find an approximate depth of the outer core (same idea as SONAR).
• Infrasound-


  Frequencies below 20 Hertz.
• Ultasound-


  Frequencies above 20,000 Hertz.
• Sound, vibrations in the air, is converted to vibrations of the ear drum. Bones in the middle ear pass these vibrations on via small windows, to the inner ear.
• When a wave reaches a boundary it changes speed and changes direction (this is refraction).
• Whether sound or light, when a wave slows down, it bends towards the normal. When it speeds up, it bends away from the normal.