Tricky P1 Topics

Tricky P1 Topics

1. Waves

   • Trasverse waves
     • The vibration is at right angles to the direction of wave travel.
     • Electromagnetic waves and water waves are transverse
   • Longitudinal waves
     • The vibration is back and forth along the direction of wave travel
     • Sound waves are longitudinal
   • Seismic waves are produced by earthquakes
     • P waves
       • Slow moving longitudinal waves
     • S waves
       • Fast moving transverse waves
     • Detected using a seisometer

2. Ultrasound and Infrasound

   • Humans can hear from 20 Hz to 20,000 Hz
     • Sound above 20,000 Hz is called ultrasound
       • Dolphins use this for communication
     • Sound below 20 Hz is called Infrasound
       • Whales use this to communicate
       • Infrasound is used to detect and moniter animal movement and volcanic activity
         • Infrasound is naturally produced by volcanoes, avlanches
   • speed of sound travels faster in solids than gases
     • Ultrasound is used for foetal scanning
       • Different body tissues reflect different amounts of ultrasound this is used to produce an image
     • Sonar is used by ships to detect the depth of water
       • Ultrasound is reflected off the bottom of the seabed
         • Distance travelled by ultrasound pulse=Speed of ultrasound x time delay
           • The answer is divided by two because it has gone to the bottom and back