The document discusses different types of waves including transverse waves, where the vibration is perpendicular to the direction of propagation, and longitudinal waves, where the vibration is parallel. It also covers characteristics of waves like frequency, wavelength, amplitude, intensity, and speed; how waves transfer energy without transferring matter; and the electromagnetic spectrum.

1. Topic 4 – Oscillations and Waves
4.3 Wave Characteristics

2. Waves
● A wave is an oscillation that can move energy
from place to place without the transfer of
matter.
● An oscillation moves no energy nor matter
overall.
● Waves can either be a pulse or a continuous
travelling wave.
● In most cases the oscillations of the particles
making up the wave can be considered to be
simple harmonic motion.

3. Types of waves
● Transverse waves
● The vibration of the
particles are at 90o
to the
direction of propagation of
the wave.
● These are seen as water
waves, surface
earthquake waves, and as
electromagnetic waves.
● Physical trasverse waves
cannot propagate in
gases.
● Longitudinal waves
● The vibration of the
particles is parallel to the
direction of propagation of
the wave.
● These are pressure
waves and are seen as
sound waves and
earthquakes.

4. Transverse Waves
Crest
Trough
Amplitude
Wavelength
x
r
Oscillations
Energy
Displacement

5. Longitudinal Waves
Compression
Rarefaction
Amplitude
Wavelength
y
x, r
Oscillations
Energy
Displacement

6. Intensity and Amplitude
● The intensity of a wave is the energy delivered
by it per second per unit area of detector.
● It therefore has units of Wm-2
● The intensity of a wave is directly proportional
to the amplitude of the wave squared.
I ∝ x0
2

7. Frequency and Period
● The period (T) of a wave is the time taken in
seconds for it to make one complete cycle.
● As most of the waves that we use have very
short periods we often use the frequency of the
wave instead.
● The frequency (f) of a wave is the number of
complete cycles in 1 second and is measured
in hertz (Hz).
f =
1
T

8. Wave Speed
● The speed with which a wave transfers energy
from place to place is known as the wave
speed.
● The distance a wave travels in one cycle is the
wavelength.
● The time taken for one oscillation is the time
period.
● The wave speed is therefore given by:
v=
x
t
= λ
T
=λ f

9. Waves in 2 Dimensions
● There are two distinct ways to describe the
motion of waves in 2 dimensions
● Rays – The wave is represented by an arrow which
lies in the direction of propagation.
● Wavefronts – The wave is represented by a series
of parallel lines that are perpendicular the direction
of propagation and show the position of each wave
crest or compression.
● Both of these methods have their uses in
specific situations and can sometimes be seen
used together.

10. Waves in 2 Dimensions
A series of wavefrontsA light ray Combined notation
The same wave in 2 dimensions

11. Transverse Waves in 2 Dimensions
● Sometimes, the direction of oscillation of a
transverse wave is shown on the ray.
Oscillations Up and Down
Oscillations In and Out
Oscillations both Up and Down
and In and Out

12. Electromagnetic Waves
● Electromagnetic waves rely on the oscillations
of electric and magnetic fields rather than
particles to move energy.
● In a vacuum, all electromagnetic waves travel
at the same speed, c = 3.00x108
ms-1

13. Electromagnetic Spectrum
● Electromagnetic waves can have any
frequency.
● The continuous spectrum of electromagnetic
waves goes from radio waves at low energy up
to high energy gamma waves
● Different wave bands are divided by their
wavelengths

14. The Electromagnetic Spectrum

15. Questions
● An electromagnetic wave has a frequency of
5.6x1012
Hz. What is the wavelength and
waveband of this radiation?
● High energy x-rays have a wavelength of 10pm.
What is the frequency of this radiation in a
vacuum?
● A red laser is fired in a vacuum. What is the
frequency of this radiation.
● A sound wave is measured to have a frequency
of 15kHz and a wavelength of 2.2cm. What is
the speed of this sound?