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ELECTROMAGNETIC
SPECTRUM
Chapter 13
LEARNING OBJECTIVES
• State that all electromagnetic waves
are transverse waves that travel with
the same speed in vacuum and state
the magnitude of this speed.
• Describe the main components of the
electromagnetic spectrum.
LEARNING OBJECTIVES
• State examples of the use of the following components:
• radio waves(eg. radio and television communication)
• microwaves(eg. microwave oven and satellite television)
• infra-red(eg. infra-red controllers and intruder alarms)
• light(eg. optical fibres fro medical uses and
telecommunications)
• ultra-violet(eg. sunbeds and sterilisation)
• X-rays(eg. radiological and engineering applications)
• gamma rays(eg. medical treatment)
WHAT IS ELECTROMAGNETIC
SPECTRUM?
Click here for introduction video to
electromagnetic spectrum
13.1 PROPERTIES OF
ELECTROMAGNETIC SPECTRUM
What is the Electromagnetic Spectrum?
• The electromagnetic spectrum consists of
electromagnetic waves of a continuous range of
wavelength/frequency.
13.1 PROPERTIES OF
ELECTROMAGNETIC SPECTRUM
13.1 PROPERTIES OF
ELECTROMAGNETIC SPECTRUM
What type of Waves are Electromagnetic Waves?
• Electromagnetic waves are transverse waves.
• The electric and magnetic fields are oscillating
perpendicular to each other and to the direction of
propagation of the wave.
13.1 PROPERTIES OF
ELECTROMAGNETIC SPECTRUM
How do Electromagnetic waves propagate?
• Electromagnetic waves transfer energy from one
place to another without the need for a physical
medium.
• Electromagnetic waves travel at a speed of
3.00 x 108 m/s in vacuum.
• All electromagnetic waves obey the laws of reflection
and refraction.
13.1 PROPERTIES OF
ELECTROMAGNETIC SPECTRUM
How do Electromagnetic waves propagate?
• The speed v of electromagnetic waves is related to the
wavelength  and frequency  by the following wave
equation:
𝑣 = 𝑓𝜆
• The frequency of an electromagnetic wave depends only on
its source. The wavelength and speed of an electromagnetic
wave depends on the refractive index of the medium in which
it is travelling.
• All electromagnetic waves except for visible light are invisible
to the human eye.
13.2 COMPONENTS OF
ELECTROMAGNETIC SPECTRUM
13.2 COMPONENTS OF
ELECTROMAGNETIC SPECTRUM
• The electromagnetic spectrum is a continuous
range of waves with extremely short wavelengths
and high frequencies at one end and extremely
long wavelengths and low frequencies at the other
end.
• The components of the electromagnetic spectrum
are classified according to increasing wavelengths
or frequencies. The frequencies determine the
amount of energy and behaviour of the type of
radiation.
13.2 COMPONENTS OF
ELECTROMAGNETIC SPECTRUM
Electromagnetic Spectrum
Gamma rays
X-rays
Ultra-violet
waves
Visible light
Infra-red
radiation
Microwaves
Radio
waves
13.2 COMPONENTS OF
ELECTROMAGNETIC SPECTRUM
How do you remember the order of
the components of the
electromagnetic spectrum?
How about a singing a song to
remember the order?
(Click Here!)
13.2 COMPONENTS OF
ELECTROMAGNETIC SPECTRUM
How do you remember the order of
the components of the
electromagnetic spectrum?
Using Mnemonic
13.2 COMPONENTS OF
ELECTROMAGNETIC SPECTRUM
Using Mnemonic
Example:
Raging Martians Invaded Venus Using X-ray Guns
EXAMPLE 1
Gamma
rays
P
Ultra-violet
Visible
rays
light
Q
Radio
waves
The diagram represents the range of radiations in the
electromagnetic spectrum.
Name the two radiations labelled P and Q.
P
:
X-ray
Q
:
Infra-red rays or Microwaves
EXAMPLE 1
Gamma
rays
P
Ultra-violet
Visible
rays
light
Q
Radio
waves
The diagram represents the range of radiations in the
electromagnetic spectrum.
Complete the following:
Compared to radio waves, gamma radiation has
__________________ frequency;
__________________ wavelength;
__________________ speed in vacuum.
13.3 APPLICATIONS & USES OF
ELECTROMAGNETIC SPECTRUM
Radio Waves
Description
 Lowest frequencies and
longest wavelengths.
 Used for transmission of
signals and data. An
antenna is used to receive
these signals.




Uses
Radio broadcasting
Telecommunication
Wireless networking
Television transmission
13.3 APPLICATIONS & USES OF
ELECTROMAGNETIC SPECTRUM
Microwaves
Description
Uses
 Easy to control and direct
 Satellite
 In a microwave oven,
communication/
broadcast
absorbed microwaves cause
water molecules in the food  For cooking food
to vibrate rapidly, which then  Remote sensing
heats up the food.
(radar)
13.3 APPLICATIONS & USES OF
ELECTROMAGNETIC SPECTRUM
Infrared waves
Description
 Produced by hot objects.
 Some animals can see in
infrared red light to enable
them to detect warmblooded animals.




Uses
Night vision
binoculars
Thermal imaging
Remote controls
Motion detectors (in
security systems)
13.3 APPLICATIONS & USES OF
ELECTROMAGNETIC SPECTRUM
Visible Light
Description
Uses
 Produced by luminous objects  Optical fibres for data
transmission
(e.g. burning items and stars
such as the Sun).
 Endoscopy (visual
 Crucial for normal human sight.
inspection of internal
organs)
 Used in data transfer in
 Photography
telecommunications and by
electronic devices such as
television sets and computer
monitors.
13.3 APPLICATIONS & USES OF
ELECTROMAGNETIC SPECTRUM
Ultraviolet rays
Description
Uses
 The human skin produces vitamin D
 Sunbeds (tanning machines
for indoor tanning)
naturally when exposed to ultraviolet
rays.
 In ‘black lights’ for medicine,
 Also causes tanning by stimulating the
forensics, lighting effects,
production of the skin pigment known as
polymerization and insect
melamine. Can cause sunburn.
attraction
 Some chemicals absorb ultraviolet
 Fluorescence effect.
radiation and then appear to be
Fluorescent objects like
glowing. This fluorescence effect is
diamonds absorb UV rays
and convert it to visible light
used to create markings on bank notes,
paints and dyes.
13.3 APPLICATIONS & USES OF
ELECTROMAGNETIC SPECTRUM
X-ray
Description
Uses
 High frequencies.
 In scanners in airports
 Able to penetrate many
to check the contents of
materials.
luggage bags
 Used in the medical field  Detecting cracks in
pipes and buildings
to obtain images of the
internal parts of our
 Radiography
bodies.
(diagnostic X-ray
images in medicine)
13.3 APPLICATIONS & USES OF
ELECTROMAGNETIC SPECTRUM
Gamma Rays
Description
 Waves with the highest frequency
and most energy.
 Dangerous rays coming from
nuclear explosions and atomic
bombs which can cause cell and
tissue injury.
 As they can cause damage to living
cells, they are used in the medical
field to kill cancer cells.
Uses
 Sterilisation of
medical
equipment
 Radiotherapy