11 - Waves 1 Flashcards
progressive wave
a wave in which the peaks and troughs, or compressions and rarefactions, move through the medium as energy in transferred
longitudinal wave
a wave in which oscillations of the medium particles are parallel to the direction of wave travel and energy transfer
transverse wave
a wave in which the oscillations of medium particles are perpendicular to the direction of wave travel and energy transfer
p-waves
primary waves - longitudinal waves that travel through the Earth from an earthquake
s-waves
secondary waves - transverse waves that travel through the Earth from an earthquake
equilibrium position
the resting position of waves or particles in an oscillation
restoring force
a force that tries to return a system to its equilibrium position
peaks
the maximum positive amplitude of a transverse wave
troughs
the maximum negative amplitude of a transverse wave
compressions
a moving region in which the medium is denser or has a higher pressure than the surrounding medium
rarefactions
a moving region in which the medium is less dense or has less pressure than the surrounding medium
displacement (of a wave)
distance from the equilibrium position in a particular direction - a vector so can have either positive or negative value
amplitude
maximum displacement from the equilibrium position (can be positive or negative)
wavelength (λ)
minimum distance between two points in phase on adjacent waves - eg the distance from one peak to the next
time period of oscillation (T)
the time taken for one oscillation, or time taken for a wave to move one whole wavelength past a given point
frequency
number of wavelengths passing a given point per unit time
wave speed
distance travelled by a wave per unit time
the wave equation
v = f λ
wave speed = frequency x wavelength
phase difference (Φ)
the difference in displacement between two oscillating objects, or the displacement of an oscillating object at different times
in phase
particles oscillating perfectly in time with each other (reach maximum displacement at the same time) are in phase
antiphase
particles oscillating completely out of step with each other (one reaches maximum positive displacement as the other reaches maximum negative displacement) are in antiphase
phase difference formula
in radians: Φ = (x/λ)2π
in degrees: Φ = (x/λ)360
x is the distance between points
wave profile
a graph showing the displacement of the particles in the wave against the distance along the wave
reflection
change in direction of a wave at a boundary between different media so that the wave remains in the original medium
law of reflection
the angle of incidence is equal to the angle of reflection
angle of incidence
angle between the direction of travel of an incident wave and the normal at a boundary between two media
angle of refraction
angle between the direction of travel of a reflected wave and the normal at a boundary between two media
refraction
the change in direction of a wave as it changes speed when it passes from one medium to another
diffraction
phenomenon in which waves passing through a gap or around an obstacle spread out
polarisation
phenomenon in which oscillations of a transverse wave are limited to only one plane
plane polarised
description of a transverse wave in which the oscillations are limited to only one plane
partially polarised
description of a transverse wave in which there are more oscillations in one particular plane, but the wave is not completely plane polarised - occurs when transverse waves reflect off a surface
unpolarised
description of a transverse wave in which the oscillations occur in many planes
intensity
the radiant power passing through a surface per unit area
electromagnetic (EM) waves
transverse waves with oscillating electric and magnetic components that do not need a medium to propagate
electromagnetic spectrum
full range of frequencies of em waves from gamma rays to radio waves
wavelength of radio waves
> 10^6 - 10^-1 m
wavelength of microwaves
10^-1 - 10^-3 m
wavelength of infrared
10^-3 - 7x10^-7 m
wavelength of visible light
7x10^-7 - 4x10^-7 m
wavelength of ultraviolet
4x10^-7 - 10^-8 m
wavelength of x-rays
10^-8 - 10^-13 m
wavelength of gamma rays
10^-10 - <10^-16 m
refractive index
speed of light in a vacuum / speed of light through the material
total internal reflection (TIR)
the reflection of all light hitting a boundary between two media back into the original medium when the light is travelling through the medium with the higher refractive index and the incidence angle at the boundary is greater than the critical angle
critical angle
the angle of incidence at the boundary between two media that will produce an angle of refraction of 90 degrees
