module 4 chpt 2 energy transfer through waves

Module 4:Gadgets Work Wonders (II)Chapter 2 Energy Transfer Through Waves

© Copyright Star Publishing Pte Ltd

Chapter 2 Energy Transfer Through Waves2.1 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?


ObjectivesDescribe 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.


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.© Copyright Star Publishing Pte Ltd

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.



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


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.© Copyright Star Publishing

Pte Ltd

Activity Book LinkActivity 2.1Making waves with a Slinky Spring


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.


Chapter 2 Energy Transfer Through Waves2.1 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?


ObjectivesUnderstand 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 twosuccessive crests or two successive troughs. Its SI unit is the metre (m).

(e) Frequency (f) is the number of complete wavesproduced per second. The SI unit is the hertz (Hz).

Activity Book LinkActivity 2.2Observing 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 highenergy has higher amplitude

thana wave transferring low energy€

Chapter 2 Energy Transfer Through Waves2.1 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?


ObjectivesState 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 inthe order of frequency or wavelength:

(a) Radio waves have the longest wavelengths andthe 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 inis 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 transportand the Electronic Road Pricing (ERP) gantriesboth 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 unitMobile phones transmit and receive information through

microwaves

Uses of Infrared WavesRemote 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 LightVisible 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 makefood through photosynthesis

Uses of Ultraviolet WavesUltraviolet 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 checkfor real bank notes

Uses of Ultraviolet WavesUltraviolet 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 raysGamma 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 LinkActivity 2.3Uses of Electromagnetic Waves

module 4 chpt 2 energy transfer through waves

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