Waves

• Waves may be either transverse or longitudinal
• The ripples on a water surface are an example of a transverse wave.
• Longitudinal waves are when the waves vibrate parallel to the direction of energy transfer.eg.sound wave
• Sound waves travelling through air are longitudinal.
• All waves transfer energy without transferring matter
• Transverse waves vibrate perpendicularly to the direction of energy transfer.e.g light
• frequency= number of waves passing a point per second, measured in hertz (Hz)
• wavespeed= frequency x wavelength (m/s)
• -Wavespeed is frequency which is the number of waves per second multiply by wavelength which is the distance travelled by full wave

  -Put a ruler on the page and take a picture of the wave

  -Measure the distance of 10 waves and divide by 10 for one wavelength

  -Mark the page and record the wave

  -Time how long it takes for 10 waves and divide by 10

  -Repeat each 3 times and take an average

  -Calculate wavespeed by frequency times wavelength
• The amplitude of a wave is the maximum displacement of a point on a wave away from its undisturbed position.
• The wavelength of a wave is the distance from a point on one wave to the equivalent point on the adjacent wave.
• period = 1 frequency

  period, T, in seconds,

  s frequency

  , f, in hertz, Hz

  The wave speed is the speed at which the energy is transferred (or the wave moves) through the medium
• Electromagnetic waves are transverse waves that transfer energy from the source of the waves to an absorber
• Radiowaves,Microwaves,Infrared,Visible Light,Ulteaviolet,x-Rays,Gamma rays


  <-increase wavelength, ->increase frequency
• radio waves – television and radio

  • microwaves – satellite communications, cooking food

  • infrared – electrical heaters, cooking food, infrared cameras

  • visible light – fibre optic communications

  • ultraviolet – energy efficient lamps, sun tanning

  • X-rays and gamma rays – medical imaging and treatments
• Some effects, for example refraction, are due to the difference in velocity of the waves in different substances.
• Radio waves can be produced by oscillations in electrical circuits.
• Ultraviolet waves, X-rays and gamma rays can have hazardous effects on human body tissue.

  The effects depend on the type of radiation and the size of the dose.

  Radiation dose (in sieverts) is a measure of the risk of harm resulting from an exposure of the body to the radiation.
• When radio waves are absorbed they may create an alternating current with the same frequency as the radio wave itself, so radio waves can themselves induce oscillations in an electrical circuit
• Ultraviolet waves can cause skin to age prematurely and increase the risk of skin cancer. X-rays and gamma rays are ionising radiation that can cause the mutation of genes and cancer.
• Changes in atoms and the nuclei of atoms can result in electromagnetic waves being generated or absorbed over a wide frequency range
• . Gamma rays originate from changes in the nucleus of an atom.
• Our eyes only detect visible light and so detect a limited range of electromagnetic waves.
• Put a ruler on the page and take a picture of the wave

  -Measure the distance of 10 waves and divide by 10 for one wavelength

  -Mark the page and record the wave

  -Time how long it takes for 10 waves and divide by 10

  -Repeat each 3 times and take an average

  -Calculate wavespeed by frequency times wavelength
• IR PRACTICAL


  Place a Leslie cube on a heat-resistant mat. Fill it, almost to the top, with boiling water and replace the lid.

  Leave for one minute. This is to enable the surfaces to heat up to the temperature of the water.

  Use the infrared detector to measure the intensity of infrared radiation emitted from each surface, or the temperature of the surface. Make sure that the detector is the same distance from each surface for each reading.