Topic 4: Waves Flashcards
Define displacement (x).
The distance the medium has moved from the equilibrium position in a specific direction (m).
Define amplitude (x₀).
The maximum displacement from the equilibrium position (m).
Define frequency (f).
The number of oscillations per second (Hz).
Define period (T).
The time for one oscillation (s).
Define wavelength (λ).
The shortest distance between two points that are in phase along a wave (m). Eg. crest to crest.
Define wavespeed (v).
The distance travelled per unit time by the energy of the wave (or by a wavefront) (ms⁻¹).
Define phase (φ).
A measure of how “in step” different particles are.
When does simple harmonic motion (SHM) occur?
SHM is a type of oscillation that takes place when the acceleration of (and the force on) an object is;- proportional to its displacement from the equilibrium position.- in the opposite direction to the displacement (i.e. towards the equilibrium position).*The motion is due to a restoring force.
If a graph of acceleration against displacement is plotted what would a straight line and negative gradient show?
- A straight line shows that acceleration and displacement are proportional.- A negative gradient shows that acceleration and displacement are in opposite directions.
Define wave.
A movement of energy through a medium.
Describe the two types of wave motion.
Longitudinal waves - the particles of the medium vibrate parallel to the direction of the energy transfer. Eg. sound, earthquake P waves. Rarefaction and compression.Transverse waves - the particles of the medium vibrate at right angles to the direction of the energy transfer. Eg. light, earthquake S waves. Crest and trough.
Define intensity.
The power per unit area received by an observer. Measured in Wm⁻².
What is the intensity of a wave related to?
It is proportional to the square of the amplitude of the wave. I∝A²It is inversely proportional to the square of the distance from the source. I∝x⁻²
Explain the two types of waves.
Mechanical waves. These require a medium to travel through. Eg. sound and earthquake waves.Electromagnetic waves. These do not require a medium to travel through i.e. they can pass through a vacuum. All electromagnetic waves are transverse and travel at the speed of light in a vacuum.
Give the order of magnitude for the electromagnetic spectrum.
(Roman Men Invented Very Useful Xray Guns)In order of decreasing wavelength: Radiowaves 10²Microwaves 10⁻³Infrared 10⁻⁵Visible 10⁻⁷Ultraviolet 10⁻⁹Xray 10⁻¹²Gamma rays 10⁻¹⁴
Define the refractive index (n).
A measure of how fast a wave travels in the medium. The higher the value of n, the slower the wave travels.
Give Snell’s Law.
n = sini/sinr*Only applies if the first medium is air. If the first medium is not air, the law given in the data booklet applies.