2. Waves are all around us!
Water waves
Sound waves
Earthquake (seismic waves)
Waves carry energy! Example:
Electromagnetic waves.

3. What is a wave?
A wave is a disturbance that travels through
space and matter, accompanied by a transfer
of energy.
Example: the surface of a pond is actually calm
until we drop a pebble. Then the surface of
the water starts to move as it is disturbed.
That disturbance spreads outwards.

4. Types Of Waves
There are two types of waves:
1. Transverse waves
2. Longitudinal waves

5.  The direction of vibration is
perpendicular to the direction of wave
travel.
 Example: water waves, electromagnetic waves

6.  The direction of vibration is
parallel to the direction of wave
travel.
 Example: sound

7. Vocabulary
Crests / trough The high points / low points in a wave
Amplitude Maximum displacement from rest position
Phase Two points that are moving in the same
direction at the same speed and having the
same displacement from rest
Wavelength Shortest distance between two points
Frequency Number of complete waves produced in 1
second
Period/Cycle Time taken to produce 1 complete wave
Wave speed Distance travelled by the wave in 1 second.

9. Sound is…..
 A form of energy
 an example of longitudinal wave
 Produced by vibrating sources placed in a
medium. (solid, liquid or gas)

10.  Any medium that has particles that can
vibrate will transmit sound.
 Solids can transmit sound best , followed
by liquid then air.
Application:
In olden days, people would hear the
ground for movement.

11.  Temperature?
 Sound travels faster in higher temperatures
 Humidity?
 Sound travels faster in high humidity
 Pressure?
 Pressure has no effect on speed of sound

12.  The human ear can only hear sounds of
frequencies between 20 Hz and 20 kHz.
 Any sound with frequency higher than
20 kHz is known as ultrasound.
 Any sound with frequency lower than
20 Hz is known as infrasound.

13.  Ultrasound is used in medical diagnosis to
obtain images of internal parts of the body.
 Commonly used in pre-natal examination.

14.  Formation of Echoes
When sound hits a hard surface, it will
“bounce” off the surface.
The sound that is reflected back to us is called
an echo.

15.  Reverberations
It is the prolonged sound due to the merging of
many echoes.
The many echoes are produced because sound
will be reflected off the different walls in a
room.

16.  Fishing boats use echoes to detect fish and
measurement of the depth of the ocean
 War ships use echoes to detect mines
 Some animals use echoes to detect obstacles
(like bats)

17.  When describing a musical note as „high‟ or
„low‟, we are actually talking about the pitch
of the sound.
 Frequency affects pitch.
 High frequency – high pitch
 Lower frequency – lower pitch
 Shorter strings or air tunnels have higher
frequency.

18.  It is the volume of a sound.
 Loudness depends on the amplitude of the
sound wave.
 Louder sounds have larger amplitudes and
vice versa.
 It is measured in decibels (dB).