Waves

• The ripples on a water surface are an example of a transverse wave.
• Sound waves travelling through air are longitudinal.
• Longitudinal waves show areas of compression and rarefaction
• Transverse waves will have oscillations perpendicular to the direction of travel. Longitudinal waves will have oscillations parallel to the direction of travel.
• Instead of matter being transferred, energy will be transferred. This means that the particles in the air and water will remain where they are, but energy will be transferred between them. So, the wave will always be what is travelling.
• label da wave

  A) peak

  B) trough

  C) amplitude

  D) wavelength

  
• The amplitude of a wave is the maximum displacement of a point on a wave away from its undisturbed position.
• The frequency of a wave is the number of waves passing a point each second.
• To calculate the frequency of a wave, use $period =$$1/ f requency$
• The wave speed is the speed at which the energy is transferred (or the wave moves) through the medium.
• All waves obey the wave equation: $wave speed =$$frequency × wavelength$ or $v =$$f λ$
• What does 'λ' stand for and what is it measured in?

  It stands for wave length and is measured in metres.
• what is frequency measured in?

  Hertz
• what is wave speed measured in and in what units?

  measured in v in m/s
• The speed of sound waves can be measured by timing how long it takes for the sound waves to travel a known distance through a medium. This can be done by using equipment such as a stopwatch, ruler, or sonic ranger.
• to measure the speed of ripples on a water surface, count the number of waves passing a point in ten seconds then divide by ten to record frequency.
• Velocity of sound is directly proportional to the wavelength. Thus, if the velocity of sound doubles when it travels from one medium to another, its wavelength also doubles.
• Sound waves can travel through solids causing vibrations in the solid.
• Within the ear, sound waves cause the ear drum and other parts to vibrate which causes the sensation of sound. The conversion of sound waves to vibrations of solids works over a limited frequency range, which restricts the limit of human hearing.
• the range of normal human hearing is from 20 Hz to 20 kHz
• Sound waves are longitudinal waves.
• Waves can be reflected at the boundary between two different materials.
• Waves can be absorbed or transmitted at the boundary between two different materials.
• Electromagnetic waves are transverse waves that transfer energy from the source of the waves to an absorber.
• Electromagnetic waves form a continuous spectrum and all types of electromagnetic wave travel at the same velocity through a vacuum (space) or air.
• label wavie

  A) radio

  B) infrared

  C) ultraviolet

  D) gamma rays

  E) long

  F) short

  G) high

  H) low

  
• Our eyes only detect visible light and so detect a limited range of electromagnetic waves.
• Radiowaves have the highest wave lengths and a low frequency
• radio waves are produced using AC , made from oscillating charges
• oscillating charges produce electric and magnetic fields
• transmitter


  objects in which charges oscillate
• how are radiowaves received?

  absorbed by a receiver
• how far can long-wave radios travel?

  half way across the world
• what reflects short-wave radios

  ionosphere
• uses of micro waves

  -satellite imagery

  -cooking
• uses of infrared radiation

  -infrared cameras

  -cooking

  -electric heaters
• use of visible light

  -fibre optic cables
• UV radiation uses


  -security ink

  -self tanning lamps

  -energy efficient lamps
• Xrays and gamma rays

  -medical imaging

  -medical treatment