Amplitude (metres,m): distance
between the rest postition and the peak
Wavelength (meters,m): distance
between a point on one wave to the
SAME point on the next wave
Frequency (Hertz, Hz): the number of
wave crests passing a fixed point in a
Types of Waves
Transverse: oscillations (vibrations)
are perpendicualr to the direction
that the energy travels
e.g Electromagnetic waves
(vibrations) are parallel to the
direction that the energy travels
e.g Sound waves
Mechanical: require a medium
to travel, cannot occur in a
e.g Sound waves
Electromagnetic: can occur in a
vacuum. Are always transverse
e.g light and transverse
Plane: Waves that form straight lines.
Can be formed by oscillating a straight
bar onto the surface of water.
Circular: Waves that are
circular in shape.
Can be formed by oscillating a single
point onto the surface of water.
Wave Speed Equation
wavespeed = frequency x wavelength
m/s = Hz x m
v = f x λ
f = v/λ
λ = v/f
1. Calculate the speed of a wave with a frequency of 3Hz
and a wavelength of 2m
3Hz x 2m = wavespeed
3Hz x 2m = 6 m/s
Angle of incidence = Angle of reflection
In a plane mirror:
Image formed in a plane mirror is
laterally inverted (left and right are switched)
upright (top and bottom are not switched)
virtual (cannot be projected onto a screen)
Diffraction is the spreading out of waves when
they pass through a gap or round the edge of
Diffraction is at most when the wavelength
is the same length as the obstacle.
The signal from a TV transmitter mast is carried by radio
waves. If there are hills between a TV reciever and the
transmitter mast, the signal may not reach the reciever.
The radio waves passing the top of the hill are diffracted
by the hill but the do not spread enough behind the hill.
The frequency range of the
normal human ears is from
about 20Hz to about 20000Hz
Sound waves are vibrations that
travel through a medium
(substance). They cannot travel
through a vacuum.
Echoes are due to sound waves
reflected from a smooth, hard surface
All electromagnetic waves can travel
in a vacuum
All electromagnetic waves travel at 3 x
10^8 m/s in a vacuum
All electromagnetic waves are
The shorter their range (due to
absorption by the atmopshere)
The less they diffract and spread out
pass through tthe
diffract less than
also carry a lot
carry a lot of
do not need to
pass though tthe
not need to
travel far or
(1m < λ<
Radiowaves. Do not
need to carry much
information but need
a larger range.
Are thin transparent fibres that are
used to transmit signals by light nd
The light rays can't escape from the fibre, making them more
When they reach the surface of the fibre, they are
reflected back into the fibre.
Optical fibres can carry much more information than radiowaves
The Big Bang Theory
The change in an observed wavelength or
frequency of a wave due to the motion of the
source of the wave
Water: duck swimming on surface of pond
Sound: screaming person running past observer
Observer hears sounds with
shorter wavelength, higher
Observer hears sounds with a
longer wavelength, lower
White light can be dispersed through
refraction into the different colours of the
The colour spectrum shows patterns of black lines called
absorption lines. This is due to some wavelengths of light
being absorbed by elements such as hydorgen
An object that is moving away from us shows this pattern of lines
moving towards the red end of the spectrum.
Edwin Hubble discovered that:
1. Light from a distant galaxy is red-shifted.
Distant galaxies are moving away from us.
2. The further away the galaxy, the greater the red-shift.
The further away the galaxy, the faster it is moving away.
The universe is expanding after exploding
from a single initial point
1. Red Shift: indicates that distant galaxies are moving
away and that the universe is expanding. If it is expanding
it must have originated as something smaller. i.e a single
2. Cosmic Microwave Background Radiation (CMBR): If there was a huge explosion
during the Big Bang there would be traces of this explosion throughout the universe.
Microwave radiation can be detected from every direction in space. It is thought thst this
was originally gamma radiation from the Big Bang. As the universe has expanded these
waves have streched to longer wavelength microwaves. It is theorised that they will
eventually stretch to become radio waves
Space, time and matter were created in
the Big Bang