amplitude is the maximumdisplacement of a vibrating particle from its equilibrium position
the wavelength is the shortest distance between twoequalpoints on a wave
frequency is the number of waves passing a point per second, measured in hertz (Hz)
wavespeed is the distancetravelled by a wave each second
a progressive wave is a wave whose oscillations travel and transferenergy
longitudinal waves are waves whose oscillations are parallel to the direction of energytravel
transverse waves are waves whose oscillations are perpendicular to the direction of energytravel
only transverse waves can be polarised
polarisation of waves: meaning all the waves are oscillating in the sameplane.
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 partialreflection
when EM waves enter a denser medium, the waves slowdown and the wavelengths are stretched
when sound waves enter a denser medium, they speedup 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
Refractiveindex (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