waves

Cards (66)

  • amplitude is the maximum displacement of a vibrating particle from its equilibrium position
  • the wavelength is the shortest distance between two equal points on a wave
  • frequency is the number of waves passing a point per second, measured in hertz (Hz)
  • wavespeed is the distance travelled by a wave each second
  • a progressive wave is a wave whose oscillations travel and transfer energy
  • longitudinal waves are waves whose oscillations are parallel to the direction of energy travel
  • transverse waves are waves whose oscillations are perpendicular to the direction of energy travel
  • only transverse waves can be polarised
  • polarisation of waves: meaning all the waves are oscillating in the same plane.
  • polarisation can be used in things such as polaroid sunglasses to reduce glare or in a camera to enhance the image.
  • transverse waves have peaks and troughs where the oscillating particles are at maximum displacement from their equilibrium position.
  • when a longitudinal wave passes through a medium, it creates a series of compressions and rarefractions
  • reflection occurs when a wave changes direction at a boundary between two different media, remaining in the original medium.
  • the law of reflection states that the angle of incidence is equal to the angle of reflection
  • refraction occurs when a wave changes direction as it changes speed when it passes from one medium to another
  • when a wave refracts there is always partial reflection
  • when EM waves enter a denser medium, the waves slow down and the wavelengths are stretched
  • when sound waves enter a denser medium, they speed up and compress
  • a wave will refract towards the normal if it slows down during refraction
  • when drawing ray diagrams, always measure angles to the normal
  • Polarisation:
    • Only transverse waves (EM)
    • Occurs when the oscillation of a wave is restricted to one place
    • Results in plane polarised waves
    • Longitudinal waves cannot polarise because the direction of energy transfer is already in one plane
  • To demonstrate polarisation of visible light, polarising filters can be used by placing two filters on top of each other and rotating one filter by 90°
  • As light passes through the filter which is polarised in one direction, the light polarised in the perpendicular direction cannot pass through, leading to a decrease in light intensity
  • Intensity:
    • Defined as the radiant power passing at right angles through a surface per unit area
    • Formula: I = P/A
    • Units: watts per metre squared (Wm^-2)
    • The intensity of light is inversely proportional to the square of the radius, and can also be related to the amplitude of the wave (intensity ∞ Amplitude squared)
  • Refraction:
    • Occurs because when a ray enters a new medium, its speed changes
    • Refractive index (n) is used to determine the angle of refraction into the medium (n =)
  • Total internal reflection:
    • Occurs at a boundary between two transparent media, with no refraction
    • All of the light incident on the boundary is reflected back into the original medium
  • Principle of superposition:
    • When two waves meet at a point, the resultant displacement of the wave at that point is equal to the sum of the displacements of the individual waves
  • Coherent waves:
    • Waves emitted with a constant and unchanging phase difference
  • Increasing the temperature increases the speed of sound due to increased particle vibrations.
  • 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
  • Progressive waves
    • The particles in the matter vibrate as the wave passes through them, but they do not move along with the wave
    • There are two types: transverse and longitudinal
  • Transverse wave
    The oscillations are perpendicular to the direction of wave travel, such as electromagnetic waves and waves on the surface of water
  • Longitudinal wave
    The oscillations are parallel to the direction of energy transfer, such as sound waves
  • 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