physics

• Progressive wave


  An oscillation that travels through matter (or in some cases a vacuum), transferring energy from one place to another, but not transferring any matter

  
• Transverse wave


  • Oscillations are perpendicular to the direction of wave travel
  • Waves have peaks and troughs at the maximum and minimum points of displacement

  
• Longitudinal wave


  • Oscillations are parallel to the direction of energy transfer
  • Waves have areas of compression and areas of rarefaction

  
• Displacement


  The distance from the equilibrium position in a particular direction
• Amplitude


  The maximum displacement from the origin
• Wavelength


  The minimum distance between two adjacent points on a wave oscillating in phase

  
• Period


  The time taken for a full oscillation of one wavelength to pass a given point
• Frequency


  The number of complete oscillations passing a given point per unit time
• Wave speed


  The distance travelled by a wave per unit time
• Phase difference


  The difference in displacement of particles along a wave, or in 2 different waves, measured in radians

  
• Calculating phase difference


  𝑥𝑥/𝜆𝜆 × 2𝜋𝜋, where x is the separation in wavelengths between the two particles

  
• Antiphase


  Particles oscillating 𝜆𝜆/2 out of step with each other
• Techniques to determine frequency

  • Using an oscilloscope to measure time taken for one full oscillation
• Reflection


  A wave changes direction at a boundary between two media, remaining in the original medium

  
• Refraction


  A wave changes direction as it changes speed, when it enters a new medium

  
• Diffraction


  The spreading out of a wave front as it passes through a gap
• Maximum diffraction occurs when the gap the wave passes through is the same size as the wavelength of the incident wave
• Polarisation


  A property unique to transverse waves where the oscillation of the wave is restricted to one plane only

  
• Longitudinal waves cannot experience polarization
• Techniques to demonstrate wave effects

  • Ripple tank
  • Polarizing filters
  • Metal grille
• Intensity of a progressive wave

  The radiant power passing at right angles through a surface per unit area

  
• Intensity of a wave is inversely proportional to the square of the radius from a point source

  
• Electromagnetic waves


  Transverse progressive waves consisting of magnetic and electric fields oscillating at right angles to each other

  
• Electromagnetic waves can travel through a vacuum and all travel at the speed of 3.0 × 10^8 m/s
• Typical wavelengths of electromagnetic waves

  • Radio waves
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet
  • X-rays
  • Gamma rays
• Refractive index

  𝑛𝑛 = 𝑐𝑐/𝑣𝑣, where c is the speed of light and v is the speed of light in the medium
• Total internal reflection


  All of the light incident on the boundary is reflected back into the original medium
• Refractive index (n)


  Can be used to determine the angle of refraction into a medium
• Total internal reflection


  • Occurs when light travels from a medium with higher refractive index to a medium with lower refractive index, and the angle of incidence is above the critical angle
  • All of the light is reflected back into the original medium
• Principle of superposition


  When two or more progressive waves meet and overlap, they superpose, producing a single wave

  
• Resultant displacement


  Equal to the sum of the displacements of the individual waves
• Constructive interference


  Individual displacements are in the same direction, adding together
• Destructive interference


  Individual displacements are in opposite directions, cancelling each other out
• Coherence


  Two waves are emitted with a constant and unchanging phase difference

  
• Interference


  The superposition occurring between two coherent waves

  
• Maximum resultant displacement


  Occurs when the phase difference is an even multiple of π
• Minimum resultant displacement


  Occurs when the phase difference is an odd multiple of π
• Investigating superposition and wavelength using sound waves

  1. Use two audio signal generators to emit coherent waves

  2. Move a microphone connected to an oscilloscope parallel to the speakers to detect regions of loud and quiet noise
• Investigating superposition and wavelength using light waves (Young's double-slit experiment)

  1. Place a laser producing monochromatic light behind a sheet with two small slits

  2. The two coherent waves produced by the slits overlap and superpose, creating alternating bright and dark fringes on a screen

  3. Use the equation λ = xd/a to determine the wavelength of the light
• Investigating wavelength using a diffraction grating


  1. Light passes through transparent slits in a diffraction grating, producing an interference pattern

  2. Use the equation dsinθ = nλ to determine the wavelength of the light