Waves

• Describing a transverse wave

  In transverse waves the oscillations are perpendicular to the direction of energy transfer

  Eg. Ripples on surface of water
• describe a longitudinal wave

  The oscillations are parallel to the direction of energy transfer

  Cause particles to be squashed closer together or pulled further apart , producing areas of compression and rarefraction in the substance

  Eg. Sound waves in air
• Mechanical waves require a medium to travel through
• What is amplitude

  Maximum displacement of a point on a wave from its undisturbed position

  Measured in metres ( m )
• What is frequency

  Number of waves passing a fixed point per second

  Measured in hertz ( Hz )
• What is period

  Time taken for one complete wave to pass a fixed point

  Measured in seconds
• What is wavelength

  Distance fromone point on a wave to the equivalent point on the next wave

  Measured in metres
• What is wavespeed

  Distance travelled by each wave per second and the speed at which energy is transferred by the wave

  Measured in metres per second
• How do we calculate period

  Period = 1 / frequency
• How do we calculate wave speed

  Wave speed = frequency x wavelength
• Electromagnetic waves are transverse waves that transfer energy from their source to an absorber
• Refraction occurs when there is a difference in the velocity of an EM wave in different substances
• EM spectrum in order from low to high frequency

  radio waves

  Microwaves

  Infrared

  Visible light

  Ultraviolet

  Xrays

  Gamma rays
• Em spectrum in order from short wavelength to long wavelength

  Gamma rays

  Xrays

  Ultraviolet

  Visible light

  Infrared

  Microwaves

  Radio waves
• Property of visble light

  Only visible lighy on EM spectrum can be seen by the eye

  Can travel in a vaccum
• refraction occurs when there is a difference in the velocity of an EM wave in different substances
• Properties of EM waves

  can be absorbed or produced by changes inside an atom or nucleus

  When electrons in an atom move down between energy levels they emit EM waves
• Property of radio waves

  Can be produced by oscillations in an electrical circuit

  When radiowaves are absorbed by a receiver ariel they may create an alternating current with the same frequency as radio waves
• Uses of radiowaves

  television and radio signals , because they can travel long distances in air and they have longer wavelengths that can bend around obstructions to allow detection of signals when not in line of sight
• Uses of micro waves

  Satellite communication , can pass through earth's atmosphere to reach satellites

  Cooking food , can penetrate into food and are absorbed by water molecules in food by heating it
• What are the hazards of radio and micro waves

  Can penetrate thebody and cause internal heating
• What are the uses of infrared

  Infrared cameras , all hot objects emit infrared waves and sensors can detect these to turn them into an image

  Electrical heaters and cookin food , can transfer energy quickly to heat
• What is the hazard involving infrared waves

  Can damage or kill skin cells
• Use of visible light waves

  Fibre optic communications - short wavelength means visible light carries more information
• Hazards involving visible light

  Can damge the retina
• Uses of Ultraviolet

  Energy efficient lights and artificial tanning , carries more energy than visible light and some chemicals used inside light bulbs can absorb UV and emit visible light
• Hazards involving UV light

  Can damage skin cells , causes skin to age prematurely and increases the risk of skin cancer and can cause blindness
• Uses of Xrays and Gamma rays

  Medical imaging , pass easily through flesh but not denser materials like bones

  Treatments , high doses kill living cells so can be used to kill cancer cells and gamma rays can also be used to kill harmful bacteria
• Hazards involving Xrays and Gamma Rays

  Form of ionising radiation snd can damage or kill cells cause mutations