Waves

avatar
Created by
Jack H

Cards (66)

  • Progressive waves transfer energy from one place to another, but not matter.
  • When a wave travels through a medium, particles are moved from their equilibrium.
  • In a transverse wave, the particle vibrations are perpendicular to the direction of the wave.
  • In a longitudinal wave, the particle vibrations are parallel to the direction of the wave.
  • Transverse waves have peaks and troughs, where the particles are at their highest and lowest points respectively.
  • Longitudinal waves consist of compressions and rarefactions, where the particles are close together and spread out respectively.
  • In a wave, displacement is the distance between a particle’s equilibrium and its current position. Amplitude is its maximum displacement on the wave.
  • The wavelength of a wave is the distance between the same point on two consecutive waves.
  • The period of a wave is the time taken for one oscillation to occur.
  • The frequency of a wave is the number of full waves passing a point per second.
  • The speed, frequency and wavelength of a wave are related by the equation v=v=fλf\lambda.
  • The frequency and period of a wave are related by the equation f=f=1T\frac 1 T.
  • A wave can be represented by distance-displacement graph, which can be used to find wavelength and amplitude of a wave.
  • Phase difference is the difference between the displacements of particles on one or multiple waves, and is measured in degrees or radians.
  • If particles reach their maximum positive and negative displacements at the same time, they are in phase.
  • If one particle reaches its maximum positive displacement as the other reaches its maximum negative displacement, then they are antiphase, with a phase difference of 180 degrees.
  • The phase difference between two points on a wave is related to the distance between the points and the wavelength by ϕ=\phi =xλ×360 \frac x \lambda \times 360.
  • A wave can be represented by a displacement-time graph, which can be used to find the period of the wave and its amplitude.
  • Reflection is when a wave changes direction at the boundary between two media.
  • The angle of incidence is always equal to the angle of reflection.
  • No properties of the wave change when it is reflected.
  • Refraction is when a wave changes direction and speed as it passes through one medium into another.
  • There is some reflection when a wave refracts.
  • If a wave slows down, it will bend towards the normal, and if it speeds up, it will bend away from the normal.
  • When entering a denser medium, sound waves usually speed up, and EM waves usually slow down.
  • The speed and wavelength of a wave change, but its frequency remains constant when it refracts.
  • When a water wave enters shallower water, it slows down and its wavelength decreases.
  • When waves pass through a gap and spread out, this is called diffraction.
  • When a wave diffracts, its speed, wavelength and frequency remain constant.
  • A wave diffracts more when the size of the gap is close to its wavelength.
  • Polarisation only allows particles to oscillate on one plane.
  • Only transverse waves can be plane polarised, as longitudinal waves only cause particle vibrations parallel to the direction of energy transfer.
  • When a wave is reflected off a surface, more waves oscillate in one plane, so the wave is partially polarised.
  • Intensity is the power passing through a unit area.
  • Intensity can be found using the equation I=I=PA\frac P A.
  • Intensity is inversely proportional to the square of the distance from the source.
  • Intensity is directly proportional to the square of the amplitude of the wave.
  • Electromagnetic waves can travel through a vacuum, as they do not need a medium.
  • EM waves are electric and magnetic fields oscillating perpendicular to each other.
  • The standard wavelengths of the EM waves in metres are:
    • Radio - 106−10−110^6 - 10^{-1}
    • Microwaves - 10−1−10−310^{-1} - 10^{-3}
    • Infrared - 10−3−7×10−710^{-3} - 7\times 10^{-7}
    • Visible - 7×10−7−4×10−77\times 10^{-7} - 4\times 10^{-7}
    • Ultraviolet - 4×10−7−10−84\times 10^{-7} - 10^{-8}
    • X rays - 10−8−10−1310^{-8} - 10^{-13}
    • Gamma - 10−10−10−1610^{-10} - 10^{-16}