3.1.1 Progressive waves
Definitions
A progressive wave is a wave that transfers energy without transferring matter. The wave
is made up of oscillations of the particles in the medium.
Amplitude is the maximum displacement of a point on a wave from its equilibrium.
Frequency is the number of complete oscillations passing a point per second. Measured in
Hz (Hertz).
Wavelength is the distance between two peaks of a wave.
Phase is how far along a cycle a wave is.
Phase difference is the difference of phases between two waves or points.
Path difference is the difference between how far two waves have travelled to get to a
specific point.
Radians
The radian is a unit of angle.
360
∘
= 2π rad
The radian is the angle subtended by an arc on a circle at the centre of the circle where the
arc length is the same as the radius.
Phase difference can be measured using an angle where 360or ∘
is one cycle.
2π rad
Equations
Speed of a wave:
CONB007
c = fλ
Where is the speed, is the frequency, and is the wavelength.
c f λ
Frequency of a wave:
1
f =
T
Where is the frequency and is the time for one oscillation.
f T
, 3.1.2 Longitudinal and transverse waves
Nature of longitudinal and transverse waves
Longitudinal
Displacement of particles is parallel to the direction of energy propagation.
The oscillations create alternating regions of compressions and rarefactions. Compressions
are where the medium is compressed and rarefactions are where the medium is spread
apart.
Longitudinal waves require a medium to travel through (e.g. air).
An example of a longitudinal wave is sound.
Transverse
Displacement of particles/fields is perpendicular to the direction of energy propagation.
The oscillations create alternating peaks and troughs which are points of maximum and
minimum displacement from the baseline.
Some transverse waves require a medium to travel through whereas some transverse waves
can travel through a vacuum.
Examples of transverse waves are electromagnetic waves (doesn't require a medium) and
waves on a string (requires a medium, the string).
Tip CONB007
Transverse waves are perpendicular (the lines in the T are perpendicular). longitudinal
waves are parallel.
Electromagnetic waves
All electromagnetic waves travel at the same speed in a vacuum.
Electromagnetic waves are formed of two oscillating fields, a magnetic field and an electric
field.
Polarisation
Transverse waves can be polarised, meaning they have a certain rotation that they oscillate
in.
Polarisers are materials that only let one polarisation through.
When polarised light passes through a rotating polariser, the intensity will change. This is
evidence that light is a transverse wave because only transverse waves can be polarised.
An application of polarisers is the alignment of aerials for transmission and reception.
Definitions
A progressive wave is a wave that transfers energy without transferring matter. The wave
is made up of oscillations of the particles in the medium.
Amplitude is the maximum displacement of a point on a wave from its equilibrium.
Frequency is the number of complete oscillations passing a point per second. Measured in
Hz (Hertz).
Wavelength is the distance between two peaks of a wave.
Phase is how far along a cycle a wave is.
Phase difference is the difference of phases between two waves or points.
Path difference is the difference between how far two waves have travelled to get to a
specific point.
Radians
The radian is a unit of angle.
360
∘
= 2π rad
The radian is the angle subtended by an arc on a circle at the centre of the circle where the
arc length is the same as the radius.
Phase difference can be measured using an angle where 360or ∘
is one cycle.
2π rad
Equations
Speed of a wave:
CONB007
c = fλ
Where is the speed, is the frequency, and is the wavelength.
c f λ
Frequency of a wave:
1
f =
T
Where is the frequency and is the time for one oscillation.
f T
, 3.1.2 Longitudinal and transverse waves
Nature of longitudinal and transverse waves
Longitudinal
Displacement of particles is parallel to the direction of energy propagation.
The oscillations create alternating regions of compressions and rarefactions. Compressions
are where the medium is compressed and rarefactions are where the medium is spread
apart.
Longitudinal waves require a medium to travel through (e.g. air).
An example of a longitudinal wave is sound.
Transverse
Displacement of particles/fields is perpendicular to the direction of energy propagation.
The oscillations create alternating peaks and troughs which are points of maximum and
minimum displacement from the baseline.
Some transverse waves require a medium to travel through whereas some transverse waves
can travel through a vacuum.
Examples of transverse waves are electromagnetic waves (doesn't require a medium) and
waves on a string (requires a medium, the string).
Tip CONB007
Transverse waves are perpendicular (the lines in the T are perpendicular). longitudinal
waves are parallel.
Electromagnetic waves
All electromagnetic waves travel at the same speed in a vacuum.
Electromagnetic waves are formed of two oscillating fields, a magnetic field and an electric
field.
Polarisation
Transverse waves can be polarised, meaning they have a certain rotation that they oscillate
in.
Polarisers are materials that only let one polarisation through.
When polarised light passes through a rotating polariser, the intensity will change. This is
evidence that light is a transverse wave because only transverse waves can be polarised.
An application of polarisers is the alignment of aerials for transmission and reception.
