Sound

Sound

1. Red shift

   • lower pitch because there is a smaller frequency but a larger wavelength when something his moving away from you
   • higher pitch when something is moving towards you because there is a higher frequency but a smaller wavelength
   • doppler effect
     • if the object is not moving relative to the observer, the observer hears the same frequency as the object emits
     • if the object is moving relative to the observer, the waves get squashed 'together' ahead of the observer so they hear a higher pitched sound as there is a higher frequency
   • the frequency of light will change if the light emitting object is moving relative to the observer.
     • in order for the light to change, the object needs to be traveling at a certain speed of light
     • travelling away from the the observer, they see a red because there is a decrease in frequency.
     • travelling towards the observer they see a blue because there is an increase in frequency
   • light from most galaxies is red shifted, this means that galaxies are moving away from us and the universe is expanding
     • scientists believe that the universe was began from a very small space sand expanded rapidly in an event called 'the big bang' (an explosion) 14 billion years ago

2. sound is caused by vibrating objects, it travels as vibrations through a medium not a vacuum.

   • it is a series of compressions, the frequency at which th object vibrates determines the frequency of the sound.

3. a greater amplitude - a louder sound

   • a greater frequency - a higher pitch

4. we can hear from 20Hz - 20,000 Hz

   • anything above that is ultrasound
     • use it for pre-natal scans, cleaning, kidney stones and sonar
     • can pass through the body but whenever they reach a boundary between tow different media some of the wave reflected back and detected. The exact timing and distribution of these echoes are processed by a computer to produce a video image of the fetes

5. echo

   • is an example of reflection of sound.

6. they can diffract, reflect and refract

   • as they enter a denser material they speed up