Waves

• Waves transfer energy from one point to another
• A Transverse Wave are particles of water that move up and down, at right angles (or perpendicular) to the direction of the energy transfer.
• A Longitudinal Wave are particles of air that vibrate backwards and forwards in the direction of the energy transfer.
• An example of a Transverse Wave is a water wave.
• An example of a Longitudinal Wave is sound.
• Frequency is the number of waves to pass a point every second.
• Humans can hear frequencies between 20 and 20,000Hz
• Ultrasound - f > 20 kHz (sounds with a frequency greater than 20,000 Hz)
• Infrasound - f < 20 Hz (sounds with a frequency less than 20 Hz)
• Speed of sound in the air is approximately 340m/s.
• Speed of sound is different in different materials. The denser the materials, the faster the sound.
• Sound Level is a measure of how loud or quiet a sound is.
• Sound Levels are measured in decibels (dB).
• Danger Level: 80 dB, Threshold of pain: 140 dB
• Light travels at 3x108m/s.
• The Angle of Incidence (i) equals the angle of reflection (r).
• Light changes speed as it travels from one medium into another.
• Light changes direction if it hits the boundary between different materials at an angle.
• Lenses -

  • Convex lens converges rays of light.
  • Concave lens diverges rays of light.
• Visible Spectrum -

  • White light is made up of ROYGBIV - the visible spectrum.
  • A prism can be used to break white light into its constituent colours.
• Electromagnetic Waves in Space -

  • Different Celestial Bodies emit different sections of the Electromagnetic Spectrum.
  • The Sun and all stars emit all the different types of radiation of the Electromagnetic Spectrum.
  • Only some radiations of the electromagnetic spectrum make it through to Earth.
  • In order to detect certain wavelengths of EM spectrum, we need to send telescopes into Earth's orbit, outside the atmosphere.
• The 7 sections of the electromagnetic spectrum are: Radio, Microwaves Infrared, Visible, Ultraviolet, X-rays, Gamma rays.