The Nature of Waves
START-UP
In this activity, you will observe the movement of a wave. Then, you will
determine the source of the wave’s energy.
1. Tie one end of a piece of rope to the back of a chair.
2. Hold the other end in one hand, and stand away from the chair so that
the rope is almost straight but is not pulled tight.
3. Move the rope up and down quickly to create a wave. Repeat this step
several times. Record your observations.
1. In which direction does the wave move?
2. How does the movement of the rope compare with the
movement of the wave?
3. Where does the energy of the wave come from?
1. In which direction does the wave move?
The wave moves from one end of the rope to the other.
2. How does the movement of the rope compare with the movement of the
wave?
Each piece of rope moves up and down, that is, in a direction different
from the wave.
3. Where does the energy of the wave come from?
The energy of the wave comes from shaking the rope. When you stop
shaking the rope, the wave eventually stops moving.
Can you think of some
examples of waves?
Waves
•Sound
•Light
•Water
•Radio
•Seismic.
What is the function of a wave?
A wave is a disturbance that carries
energy from one place to another.
A wave does NOT carry matter with
it! It just moves the matter as it goes
through it.
A wave transmits energy from one place to another.
For example, energy can be carried by a water wave
generated by a boat out at sea to the shore, or by a sound
wave from the loudspeaker to an audience’s ears.
The most common waves found in daily life are water
waves, sound waves and electromagnetic waves.
Some waves do not need matter (called a
“medium”) to be able to move (for example,
through space).These are called
electromagnetic waves (or EM waves).
Some waves MUST have a medium in order to
move. These are called mechanical waves.
TYPES OF WAVES
WAVES
Mechanical waves
Transverse waves
Electromagnetic waves
Longitudinal waves
Transverse waves
Mechanical Waves
 Require matter to travel through
 The matter the mechanical wave travels
through is called a MEDIUM
 Examples of a medium that a mechanical
wave can travel through: sound waves,
earthquake waves, water waves
Electromagnetic waves
 Energy transfer without going through a
medium.
 Examples include: Microwaves, Visible light,
TV and radio signals, and X rays
 Although electromagnetic waves do not need
a medium, they can go through matter, such
as air, water, and glass.
 The energy that reaches Earth from the sun
comes through electromagnetic waves,
which go through space.
Wave Types
Mechanical
Electromagnetic
e.g. Water waves, waves on a e.g. Radio, X-Rays, Light
rope, sound
Must have a substance to
travel through
Does not need a substance to
travel through but can travel
through various substances
Cannot travel in a vacuum
Can travel in a vacuum
Vibrations passed on from
molecule to molecule
Travel at very fast speed in a
vacuum: 3 × 108 m/s
Quiz
1. A wave is a disturbance that travels through _____ or
(space, matter)
_____.
(energy)
2. A wave carries _____.
3. Waves that require a medium are called
(mechanical)
_________waves.
4. Waves that do not require a medium are called
(electromagnetic)
____________________waves.
• All waves transfer energy by repeated vibrations.
• Based on the direction in which the particles of the medium
vibrate compared with the direction in which the waves
move.
• The two main types of waves are transverse waves and
longitudinal waves.
A part of a longitudinal wave where the particles are
crowded together is called a compression.
A part where the particles are spread apart is a
rarefaction