Describing transverse waves
and the wave equation
Lesson Objectives:
To be able to identify amplitude, wavelength
and frequency on a diagram of a transverse
wave.
To be able to use the equation for wave
speed
JCX - Y11 W+R

REMEMBER LAST LESSON….
• We cannot see light or sound waves so looking
at waves moving along a spring can help us
learn more about them.
• There are 2 main types of waves, they carry a lot
of energy from one place to another.
• The 2 types are called TRANSVERSE AND
LONGITUDINAL waves.
JCX - Y11 W+R

TRANSVERSE AND
LONGITUDINAL
• TRANSVERSE • LONGITUDINAL
WAVES WAVES
• The wave moves at • The wave moves
right angles to the along in the same
disturbance or direction as the
vibration. disturbance or
vibration.
JCX - Y11 W+R

V Wavelength
i
b Amplitude
r
a
Amplitude
t
i Wavelength
o
n Direction of travel
JCX - Y11 W+R

V Wavelength –
Peak to Peak
i
b
r
a
t
i Wavelength –
o Trough to Trough
n Direction of travel
JCX - Y11 W+R

Height
(m)
Frequency – The number of
waves per second. If one wave
2 passes in one second it has a
frequency of one Hertz or Hz. This
is the unit of frequency.
1
0
Time (s)
1 2
1
2
JCX - Y11 W+R

How fast do waves travel?
• You can work out the speed of a wave if
you know…..
1. How many waves pass each second.
(the frequency).
2. How long each wave is.
(the wavelength)
JCX - Y11 W+R

The wave equation
WAVE SPEED = FREQUENCY X WAVELENGTH
(m/s) (Hz) (m)
Hz is short for HERTZ which is the unit of
measurement for frequency.
JCX - Y11 W+R

The wave equation
• Example:
• Frequency = 165Hz
• Wavelength = 2m
• What is the wave speed?
Wave speed = frequency x wavelength
Wave speed = 165Hz x 2m
Wave speed = 330m/s
JCX - Y11 W+R

• Find the wave speeds….
THREE STEPS TO EXAM MARKS
• 1) Wavelength = 3m,
Frequency = 100Hz
• 2) Wavelength = 2m,
Frequency = 135Hz Write out the equation in full
Rearrange it if you need to using your
• 3) Wavelength = 0.5m, Formula triangle
Frequency = 200Hz
• Remember the 3 step method Put in the numbers you have been given
In the question.
for equations – YOU MUST DO Check they are in the correct positions.
THIS TO GET FULL EXAM
MARKS!!
Do the calculation.
Write the answer clearly and
Don’t forget the UNITS.
JCX - Y11 W+R

m/s
Wave Using your formula
speed triangle means you can
work out what equation
to use if you need to
find wavelength and
frequency.
Frequency x wavelength
Hz m
JCX - Y11 W+R

Further Work
• Complete questions................from your
text book.
• HOMEWORK
• How could you measure the speed of
water waves. Plan an investigation to
show how this can be done.
JCX - Y11 W+R