# INTRODUCTION TO WAVES

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```					INTRODUCTION TO WAVES

What is a Wave?

Lesson Overview

• In this lesson, students will learn the
concepts/terms used in wave propagation.
• Discussion will then focus on the
classification of waves
• Briefly look at the effects of hole size in
relation to wavelength in diffraction of
water waves (An introduction into wave
properties)

Review of Waves
Wave terminology
1. What are Mechanical Waves? Answer: Mechanical
Waves are waves which propagate through a
material medium. A medium is any material that
allows wave propagation. Examples are solid, liquid
or gas

2. Give two basic types of wave motions for
and transverse waves

NOTE THE DIFFERENCE
• Distinguish between longitudinal and
transverse waves.
• Answer: In a transverse wave, the motion
of the medium is perpendicular to the
motion of the wave.

• In contrast to transverse waves, longitudinal are
waves in which the medium moves back and
forth in the same direction as the motion of the
wave.
Examples of Transverse Waves
• Water waves are known as transverse waves obviously
because the motion of the water is up and down, or at
right angles to the direction in which the waves are
travelling.
Other known examples are
• light waves, and
• heat waves

Examples of Longitudinal Waves

• Sound waves are longitudinal waves

• Why is sound wave classified as a
longitudinal wave?

• This is because sound waves travel back
and forth in the same direction as the
wave motion.
Sound Wave – A Classic Example

• As a sound wave is propagated and
moves out of a loud speaker to the ear
of a listener, particles of air vibrate
(are disturbed) back and forth in the
same direction and the opposite direction
of energy transport.

Mechanical and Electromagnetic Waves

• What is an electromagnetic waves?
An electromagnetic wave is a wave which
is capable of transmitting its energy
through a vacuum ( a vacuum is an empty
space).

What is a Mechanical Wave?

• A mechanical wave is a wave which is not
capable of transmitting its energy through a
vacuum (empty space)
• Mechanical waves require a medium in order
to transport their energy from one place (the
source) to another.
• Obviously sound cannot be transmitted in a
vacuum hence a sound wave is an example
of a mechanical wave.

• Diffraction is one of the most interesting,
and also very useful, properties of waves.
• What happens when water wave strikes a
barrier with a hole?
• A part of the wave can move through the
hole. Note: The part of the wave that
strikes the wall will not move forward
• Note: Diffraction can only take place if
the hole in the barrier is similar in size to
the wavelength of the wave.
ANIMATIONS OF WATER WAVES

•   Log on to the web address shown below to see Diffraction of water wave animation
•   http://www.ngsir.netfirms.com/englishhtm/Diffraction.htm

•   Log on to the web address shown below to see interference of water wave animation
• http://www.ngsir.netfirms.com/englishhtm/Interference.htm

HOMEWORK/ASSESSMENT

• Suggested Student Assessment:
• Ask the students to research the
characteristics of mechanical waves.
• Distinguish between light waves and
sound waves
In our next lesson we shall be looking at
the unique nature and properties of
different wave types