Physics- Waves

• In science a wave is an oscillation or vibration that transfers energy of data. A wave can also be an undulation on the surface of water.
• All waves have three important features:

  • An amplitude = Distance from the middle to the top or bottom of a wave
  • A frequency = number of waves that go past a particular point per second
  • A wavelength = Distance from one point on a wave to the same point on the next wave
• The top a wave is called a peak or creat and the bottom of the wave is called a trough
• A transverse wave is a wave traveling perpendicular to the direction of the wave (or at right angles).
• A longitudinal wave has Oscillations parallel to the direction of energy transfer.
• Sound waves are longitudinal waves, which means they travel through matter by compressing it as they pass through.
• Light waves are transverse waves, which means they travel through space without any medium.
• Longitudinal wave:

  In a compression, the waves’ particles are closest together and in rarefaction, the waves‘ particles are furthest apart.
• Waves bounce off surfaces and barriers this is called reflection.
• The wave coming into the barrier = Incident wave

  The wave bouncing off = reflected wave
• When waves are in step with each other, the add up, this is called superpose. When waves aren’t in step with each other the cancel out, they cancel out and you get less than you had before.
• Reflection occurs when a wave hits an object that does not allow the wave to pass through it. The wave will then be reflected back from where it came.
• Sound travels:

  In air= 340 m/s

  In water= 1500 m/s

  In solids= 5000 m/s
• The speed of light is faster than the speed of sound.
• The larger the amplitude the higher the sound. To make a louder sound sound you need a bigger vibration.
• The pitch of a noise depends on the frequenc, the higher the frequency the higher the pitch. Frequency is measured in hertz (Hz) or Kilohertz (KHz).
• To make a higher pitch you need to make the thing vibrate faster so there are more waves per second.
• You can only hear a particular range of frequencies called the audible range. You have the largest audible range when you are young (20-20000Hz). Your audible range decreases as you age.
• Your ear detects sound waves.

  The pinna directs the sound into your auditory canal towards your ear drum.

  The Pinna, Auditory canal and eardrum make up your outer ear.
• Your ear drum vibrates and passes the vibration on to the ossicles (Hammer, Anvil and Scapil). The ossicles are are tiny bones that amplify sound and they make the oval window vibrate.
• After the oval window is vibrates, the vibration is passed onto liquid in the cochlea. This contains thousands of tiny hair cells. As the liquid moves the hairs move. Specialized cells at the base of the hairs convert the movement into an electrical signal. The signal travels down the auditory nerve to your brain to be processed.
• The cochlea and the semi-circular canals make up the inner ear. The semi-circular canals help you to balance.
• You measure sound intensity in decibels (dB). The decibel scale is not linear or like a ruler but each increase is 10 times greater than the previous one. E.g: A 40 dB sound is 100 times more intense than a 20 dB sound
• Your hearing can be damaged:

  • By sharp objects making a hole in your eardrum but your eardrum will grow back
  • A build-up of ear wax
  • Very loud sounds
  • Head injuries
• How does a microphone work?

  When a singer sings into a microphone the sound waves hits a flexible plate called a diaphragm. The diaphragm vibrates, like you eardrum and produces an electrical signal just like the cells in your cochlea. The signal Carries the information that the sound carried.
• You can use an amplifier make sound louder.
• Loudspeakers convert the electrical signal back into sound when they vibrate.
• When sound reflects off a surfaces it produces an echo.
• Sound takes time to travel. There is a time delay between making a loud sound and hearing the echo.
• If lots of echoes join together to produce a longer sound, this is called a reverberation. You can reduce the effects of echoes by covering the walls with soft materials and putting carpet on the floor.
• Ultrasound is a frequency above 20,000 Hz. When doctors make images of unborn babies the ultrasound wave travels through the woman and reflects of the fetus. The machine detects the echo and it uses the time taken for the echo to build up to create an image.
• Uses of Ultrasound:

  • In physiotherapy reduces pain and swelling in the tendons.
  • On ships, a transmitter under the ship sends out a wave to travel through the sea and reflect off the seabed. A receiver detects the time taken for the reflection to work out the depth of the water.