Waves Flashcards
Define
displacement
(in terms of waves)
Distance of a particle from its original/undisturbed position
Define
amplitude
The maximum displacement of a particle from its undisturbed/equilibrium position
Define
phase difference
The difference between the vibrations of two oscillating particles, i.e. the amount by which one oscillation leads or lags behind another, expressed in degrees or radians.
Define
period
(in terms of waves)
Time take for one complete oscialltion of a point on a wave
Define
frequency
Number of oscillations per unti time, measured in Hertz (Hz)
f = 1/T
Define
wavelength
For a progressive wave, it is the distance between any two successive particles that are in phase, e.g. it is the distance between 2 consecutive crests or 2 troughs.
Define
wave speed
Speed at which the waveform travels in the direction of the propagation of the wave
Deduce, from the definitions of speed, frequency and wavelength, an equation linking the three.
Speed = Distance / Time
A wave travels a distance of one wavelength, λ, in a time interval of one period, T.
The frequency, f, of a wave is equal to 1 / T
Therefore, speed, v = λ / T = (1 / T)λ = fλ
v = fλ
Define
progressive wave
A wave that transfers energy from one place to another.
Define
intensity
(in terms of waves)
The rate of energy transfer (power) transmitted normally to the direction of wave propagation through a surface per unit area:
intensity = power/cross-sectional area
intensity ∝ (amplitude)2
Unit: W m−2.
Compare transverse and longitudinal waves
Tranverse:
- Oscillation of wave particles perpendicular to direction of propagation
- Polarisation can occur
- E.g. light waves
Longitudinal:
- Oscillations of wave particles parallel to direction of propagation
- Material through which it travels is alternately compressed (compression) and expanded (rarefaction)
- Polarisation cannot occur
- E.g. sound waves
Define
polarisation
When oscillations are confined to one direction in a plane, {NOT just “in one direction”} normal to the direction of propagation.
State the properties of electromagnetic waves
- propagated by oscillating electric and magnetic fields oscillating at right angles to each other
- travel with a constant velocity of 3 x 108 ms-1 in vacuum
- not deflected by electric or magnetic fields
- can show interference or diffraction.
- transverse waves
- can be polarised
- need no medium of propagation i.e. can travel in a vacuum
List the principal radiations of the electromagnetic spectrum in order of increasing wavelength
- gamma rays
- X-rays
- ultraviolet
- visible light
- infrared
- microwaves
- radiowaves
What is the wavelength range of:
gamma rays
10-16 to 10-10m
