(waves)

• waves transport information and energy in a medium without transmitting mass, transmissions are done by a vibration of the medium
• 2 types of waves:

  • transverse (90 degree to the direction of transfer)
  • longitudinal (along the direction of transfer)
• all waves can reflect, refract, diffract, and interfere
• sound is a longitudinal wave that is caused when an object vibrates. it travels in air, better in liquids, and the best in solids (molecules are closely packed)
• a greater frequency of sound waves means a higher pitch (short wavelength) a greater amplitude means greater energy, louder sound
• velocity = frequency x wavelength (wavespeed)
• frequency = 1/time
• doppler effect is when an object moves towards and away, there is a change in the observed sound. (wave frequency) When thee object moves towards, the waves at front are compressed, so there is a higher pitch. When the object moves away, the waves at the back are longer, so there is a lower pitch. (red shift = receding, blue shift = approaching)
• law of reflection is that the angle of incident = the angle of reflection
• refraction is caused by a change of speed through a different medium which causes a change of direction (A to G come to me, G to A go away)
• snells law = sin i / sin r

  sin i / sin r = n (refractive index)
• critical angle is an angle that refracts along the barrier of a medium. total internal reflection is any angle after the critical angle
• the visible spectrum has 7 colours (ROY G BIV) red is refracted the most, violet the least
• all electromagnetic waves travel at the speed of light (different speeds in different mediums)
• 7 electromagnetic spectrum waves (order of least to most energy)

  1. radio
  2. micro
  3. infra-red
  4. visible (ROY G BIV)
  5. ultra violet
  6. x rays
  7. gamma
• frequency is the number of waves that pass a single point per second (measured in hertz Hz)
• when a wave enters a denser medium, the speed decreases and bends towards the normal. if the wave enters a less dense medium, the speed increases and bends away from the normal
• uses of electromagnetic waves:

  1. radio (radio and television communication)
  2. micro (satellite transmissions and cooking)
  3. infrared (heaters and night vision)
  4. visible (optical fibers and photography)
  5. ultraviolet (fluroescent lamps)
  6. x-ray (x-ray imaging)
  7. gamma (sterillising food and medical equipment)
• dangers of electromagnetic waves:

  1. radio
  2. micro (heating of internal body tissues)
  3. infrared (skin burns)
  4. visible
  5. ultraviolet (skin cancer)
  6. x-ray (cancer)
  7. gamma (cancer and mutations)
• all electromagnetic waves travel at the same speed of light in a vacuum. in different mediums, they have different speeds
• light waves are transverse, and can reflect, refract, and diffract
• an optical fibre is a glass rod which uses total internal reflection to transport information by light
• diffraction is the spreading out of waves as they pass through oor around objects