P1 - Waves and Radiation

• A longitudinal wave has particles that vibrate in the direction of the wave
• Transverse waves have particles that vibrate perpendicular to the direction of the wave
• The speed of an electromagnetic wave is determined by its wavelength and frequency, with shorter wavelengths having higher frequencies.
• Reflection is when a wave hits a surface and bounces off at the same angle
• A refraction is when a wave goes from one medium to another at a different speed
• Wavespeed = Frequency x Wavelength
• Frequency is the number of waves passing in a second. It is measured in Hertz (Hz)
• A period is the time it takes for one whole wave to pass
• The EM spectrum is the range of frequencies that can be used to transmit electromagnetic waves.
• Radiowaves have a long wavelength but a low frequency and are used in radio TV and have no risks
• Microwaves are used in sattelites, cooking, and mobile phones and have the risk of generating heat
• Infra Red is used to cook/warm food and TV remotes and have the risk of burning
• Visible light is used in fibre optic, photography, television, and computer screens and have the risk of damaging eyes due to brightness of the light
• Ultra Violet is used in sun beds, energy-efficient light bulbs and detergents and the risks are that it can cause cell damage, cancer and loss of sight
• X-rays are used in X-ray/CT scans and gamma rays are used to destroy hidden tumours, sterilisation and tracing of dieases. Both are ionising so the risks are that they cause mutations and cancer
• EM Spectrum(from longest wavelength and low frequency to shortest wavelength and high frequency):

  • Radio waves
  • Microwaves
  • Infra-red
  • Visible light
  • Ultra-violet
  • X-rays
  • Gamma rays
• The ripple tank experiment is used to measure the wavelength and frequency.
• Instructions on ripple tank:

  1. Set up equipment
  2. Switch on moter + lamp
  3. Use a ruler and measure the wavelength
  4. Count waves per second (could use strobe to count)
• Results of ripple tank:

  • Turning the moter up makes the waves more frequent and the wavelength shorter
  • Wavespeed remains the same
• Problems and solutions of ripple tank:

  • Unclear shadows -> Use a brighter lamp or make room darker
  • Inaccurate wavelength -> Take a picture
  • Inaccurate frequency -> Take a video then slow it down
• Refraction occurs when a wave changes speed as it passes through different mediums. The angle of incidence is equal to the angle of refraction.