Waves

• Longitudinal parallel (sound)


  Waves that vibrate in the same direction as the direction of travel
• Transverse


  Waves that vibrate perpendicular to the direction of travel
• Amplitude


  Maximum height above or below the midline of a wave
• Right angle (water light heat)
• Frequency


  Number of complete waves to pass a point every second
• Period


  Time taken for one complete wave to pass a point
• Waves transfer energy without transferring matter
• Reflection: Angle of reflection = Angle of incidence, no change in wave
• Refraction


  Change in speed of a wave when it travels from one medium to another, can also change direction
• Electromagnetic spectrum


  • Radio
  • Microwave
  • Infrared
  • Visible light
  • Ultraviolet
  • X-ray
  • Gamma ray
• Radio wave


  Large wavelength, low frequency, used for broadcasting and communications
• Microwave


  Used for cooking and satellite transmissions
• Infrared


  Used for heaters and night vision equipment
• Visible light


  Used for optical fibres and photography
• Ultraviolet


  Used for fluorescent lamps
• 1. ray

  Used for medical applications and internal structure of objects, also used for sterilising
• Gamma ray


  Used for medical applications and sterilising, but can cause cancer and mutations so protective measures are needed
• More dense medium = light bends towards the normal, less dense medium = light bends away from the normal
• Critical angle


  Angle of incidence where the refracted light travels along the boundary between the two media
• Total internal reflection


  When the angle of incidence is greater than the critical angle, the light is totally reflected back into the more dense medium
• Uses of total internal reflection


  • Periscopes
  • Bicycle rear reflectors
  • Fibre optics
• Fibre optics consist of two layers of different types of glass, where light entering the inner glass is totally internally reflected all the way down
• Fibre optics are used for broadband communication as they can carry more information and are more secure
• Fibre optics are used in endoscopes, with one fibre transmitting light and the other returning an image
• Dispersion

  When white light passes through a prism, the different wavelengths (colours) refract at different angles, separating the light into its spectrum
• In the spectrum, red light has the lowest refractive index and is at the top, while violet light has the highest refractive index and is at the bottom
• wave speed = frequency x wavelength
• frequency = 1/time period
• refractive index = sin(angle of incidence)/ sin (angle of refraction)
• sin (critical angle) = 1/ refractive index
• efficiency = useful energy output/ total energy output x 100%