Module 4 chpt 2 Energy Transfer through Waves

Module 4:
Gadgets Work Wonders (II)
Chapter 2 Energy Transfer Through Waves
1© Copyright Star Publishing Pte Ltd

Chapter 2 Energy Transfer
Through Waves
2.1 How can a wave be produced
using a rope or a spring to transfer
energy?
2.2 How can a wave be described?
2.3 What are the different types of
electromagnetic waves and their
uses?

Objectives
 Describe what is meant by wave
motion as illustrated by vibrations in
ropes and springs
 Show understanding that waves
transfer energy

What is a wave?
 A wave is made up of motion that
repeats itself after a period of time.
© Copyright Star Publishing Pte Ltd 4
The Kallang Wave is formed when supporters take turn to stand up, raise their
hands and sit down. When done with the correct timing, these motions will
form a wave that goes round the stadium in a spectacular manner.

What is a wave?
 When a moves his hand up and down continuously, a series
of waves are formed and the waves move from left to right.
 The kinetic energy from the movement of the hand is
transferred through the rope to the fixed end.
 The rope is the medium through which the wave travels.
 If a ribbon is tied at one point of the rope, the ribbon will be
seen moving up and down but not to the right.
 A wave transfers energy through vibrations without
transferring any part of the medium.

What are the Types of Wave
Motion?
 A wave motion can be produced using a
slinky spring by moving one end up and
down while keeping the other end fixed.
 Energy is transferred from the vibrating
end to the fixed end.

Motion?
 The direction of vibration (up and down) is
perpendicular to the direction of the wave
(left to right).
 Examples of waves that move in this manner
are water waves and light waves.
circular water waves

Motion?
 Another type of wave motion can be produced
with a slinky spring by moving one end of the
spring back and forth while keeping the other
end fixed.
 In this setup, energy is also transferred from the
vibrating end to the fixed end.
Activity Book Link
Activity 2.1
Making waves with a
Slinky Spring

Motion?
 A series of dark and light bands are formed.
 The dark bands are parts of the coil which are being
compressed and the light bands are parts of the coil
which are extended.
 The direction of vibration is parallel to the direction
of the wave. An example of a wave that moves in this
manner is a sound wave.

Through Waves
2.1 How can a wave be produced using
a rope or a spring to transfer energy?
uses?

Objectives
 Understand the terms frequency,
wavelength, and the amplitude of a
wave

Terms to describe Waves
(a) Crests are the highest points of a wave.
(b) Troughs are the lowest points of a wave.
(c) Amplitude is the maximum displacement from
the rest position. Its SI unit is the metre.

Terms to describe Waves
(d) Wavelength (λ) is the distance between two
successive crests or two successive troughs.
Its SI unit is the metre (m).
(e) Frequency (f) is the number of complete waves
produced per second.
The SI unit is the hertz (Hz).
Activity Book Link
Activity 2.2
Observing Water Waves

Amplitude of a wave
 The amplitude of a
wave is related to the
energy which it
transfers. The greater
the energy a wave
transfers, the larger
its amplitude.
 The wave of a loud
sound has a larger
amplitude than the
wave of a soft sound.
a wave transferring high
energy has higher amplitude than
a wave transferring low energy€

Through Waves
2.1 How can a wave be produced using
a rope or a spring to transfer energy?
uses?

Objectives
 State how the following types of
waves are used for daily situations: (i)
radio waves (ii) microwaves (iii)
infrared (iv) light (v) ultraviolet (vi) X-
rays and (vii) gamma waves

Electromagnetic Waves
 Electromagnetic waves consist of gamma rays, X-
rays, ultraviolet, infrared, visible light, microwaves
and radio waves.
 These waves form the electromagnetic spectrum.
 In the EM spectrum, the EM waves are arranged in
the order of frequency or wavelength:
(a) Radio waves have the longest wavelengths and
the lowest frequencies.
(b) Gamma rays (γ-rays) have the shortest
wavelengths and the highest frequencies.

The electromagnetic
spectrum

Uses of Radio Waves
 Radio waves are the EM waves that transfer
music from the radio station to your radio set.
 Besides radio broadcasting, radio waves are
also used for TV broadcasting, radar and
global positioning systems (GPS).
radio waves are used in
is radio broadcasting
global positioning systems
use radio waves

Uses of Radio Waves
 Radio waves have also brought us many
conveniences by making it possible to go
wireless.
 The EZ-Link fare card for taking public transport
and the Electronic Road Pricing (ERP) gantries
both use radio wave technology.
EZ-Link fare card
ERP gantries

Uses of Microwaves
 In a microwave oven, the microwaves cause the
water particles in food to vibrate, creating
friction which heats up the food in a short time.
 Besides cooking, microwaves are also used in
mobile phone and satellite communication.
microwave oven TV remote control unit
Mobile phones transmit and
receive information through
microwaves

Uses of Infrared Waves
 Remote control units use
infrared waves to transmit
information to the television
set.
 Infrared waves are also
known as heat waves.
 The infrared thermometer
measures the amount of
infrared waves given out by
our body to determine our
body temperature.
infrared thermometer

Uses of Visible Light
 Visible light is the
only type of EM wave
that we can see. The
colours that we see
are actually light
waves of different
wavelengths.
 Light is also used by
plants for
photosynthesis and
for high speed data
transmission through
optical fibres.
plants need light to make
food through photosynthesis

Uses of Ultraviolet Waves
 Ultraviolet waves
is used in forgery
detector.
 Ultraviolet waves
in sunlight cause
our bodies to
become tanned
and help our
bodies produce
vitamin D.
ultraviolet is used to check
for real bank notes

Uses of Ultraviolet Waves
 Ultraviolet is to
kill microbes
and sterilise
medical
equipment.
 Overexposure
to ultraviolet
which can cause
skin cancer.
an ultraviolet steriliser
ultraviolet causes tanning

Uses of X-rays
 X-rays are used to produce images of
the body’s internal organs and bones.
 X-rays are also used in airports to scan
luggages for prohibited items.
doctor studying an X-ray film

Uses of Gamma rays
 Gamma rays are
used in radiation
therapy. These high
energy rays are
directed at cancer
cells to kill them.
 Gamma rays can
also be used to
sterilise medical
equipment.
international radiation hazard sign
Activity Book Link
Activity 2.3
Uses of Electromagnetic Waves

Module 4 chpt 2 Energy Transfer through Waves

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