WAVES AND THE
Electromagnetic waves perpendicular
waves combing the electric and magnetic
Electromagnetic waves are produced when
an electric charge vibrates or accelerates
and can travel through empty space or
X – rays
Diagram of Electromagnetic Spectrum
(including the relationship between frequency
Speed of Electromagnetic Waves
All electromagnetic waves travel at 3.0 x 108
m/s in a vacuum.
Speed of a wave formula:
Speed = Frequency x Wavelength
As the frequency increases, the wavelength
Includes the following types of waves
Hence this is the complete EM wave spectrum (the waves below in
ascending order of wavelength;
descending order of frequency )
Microwave Radio wave
Longitudinal Waves Transverse Waves
Overview of EM waves
Gamma rays have the shortest
wavelengths and highest
frequencies in the EM spectrum.
It is generated by :
Changes in energy levels in the nucleus
Some radioactive substances and certain
nuclear reactions produce gamma rays.
Because of their great penetrating
ability, gamma rays can cause serious
illness. However when used in controlled
conditions, gamma rays is useful in cancer
Uses of Gamma Rays
Kill cancer cells
Study the nucleus
Gamma rays are the highest
energy electromagnetic wave.
They usually come from
radioactive elements or stars
Killing cancer cells
Making pictures of the brain
Inspection tools in industry
X rays is generated by :
a) Rapid deleceration of fast moving
b) Changes in energy of innermost orbital
X-rays are used for :
• diagnostic tool in dentistry and medicine.
Doctors and dentists can examine the
condition of a person’s bones, the root of
this teeth or the state of other inner part of
• Custom officers at airports inspect the
content of your luggage using X-rays.
• Industry wise, it is used to find cracks in
structures just like cracks in bones.
X-Rays have high energy and can penetrate
Too much exposure can damage
living tissue or even cause cancer.
X - Rays
X-Ray radiation has a high
…………………….. ability and
can pass right through our
X-rays film forms images
depending on the
………………….. of the X-rays
falling on it.
The ……………….. left by things
that the X-rays can't travel
through (like bones or metal)
form the …………… on medical
Over exposure can cause
Uses of X-rays
Take ‘pictures’ of
bones in the body
Study the crystal
structure of crystalline
Check for cracks in
UV Light that is at a higher frequency and
energy than violet light.
UV light can kill micro-organisms.
Too much exposure can cause:
Sunburn, Wrinkles, and skin cancer
As it damages cell DNA
The main source of ultra-violet radiation is sunlight and it is this radiation
which gives rise to suntan and also sunburn.
Ultra-violet radiation is used in hospitals to sterilize the surgical
instruments and operating theatres as it kills bacteria and viruses.
UV can be detected by:
a) Photographic plates
b) Photoelectric cell
Uses of Ultraviolet
Gives the clothes a
‘glow’ effect in
Visible light is made up of the various ..................... of
The ……… is determined by the frequency of the light.
When electromagnetic radiation of this frequency falls
on our ……………. our brain interprets it as colour.
Visible light is the part of the EM
spectrum which can be detected by the
The visible light has its own spectrum
which consist of the 7 colours of light :
Red Orange Yellow Green Blue Indigo
An example of visible light is the
colourful laser light or the light from a
Some of the uses of light is in
optical fibres in medicine and
Our eyes detect
electromagnetic energy in a
small portion of the
called the visible light region.
The visible light region
corresponds the wavelengths
and frequencies of
red, orange, yellow, green, bl
ue, indigo, and violet light.
Uses of Visible Light
Enable us to see
Heat can be transferred through infrared
We often think of infra red as being the same
thing as 'heat', because it makes our skin feel
Most of you might have seen infra-red waves in use
during the SARS period. (picture on the top right hand
corner). It shows a thermo-detector which is placed
outside hospitals/airport to identify the warm and cool
parts of a person by analyzing infra-red radiation
emitted from the person’s body. And through this we
can see if someone is having a fever.
Infra red is useful for:
- For navigation through fog & haze as it is less
easily scattered compared to visible light
- Medical treatment : to warm injured muscles/sports
Uses of Infra-red
Infrared image of a human body. Red is hot, blue is cool.
Infrared waves are heat waves.
All objects emit infrared waves because all objects
Night vision goggles detect infrared waves and allow
the user to see the movement of objects in the dark.
Many TV remotes use infrared.
One of their most common uses is in
microwave ovens. When you switch on
a microwave oven , it gives off
electromagnetic waves that bounce
around inside the oven, penetrating the
food. Water molecules in the food
absorb the energy from the
microwaves, causing the food to get hot.
Other uses of microwaves:
a) Radar communication (as it is not easily
blocked of by buildings/trees)
b) Analysis of fine details of molecular and
c) Useful demonstration of all wave
properties on macroscopic scale
d) Telephone communication (mobile
Uses of Microwaves
Analysis of the
Radio waves are the electromagnetic waves
with the longest wavelengths and lowest
Like all electromagnetic waves, radio waves
can travel through a vacuum. However
most of the radio waves we receive have
traveled through air. Take the radio as an
example. The radio converts the
electromagnetic waves into the sound
that comes out of the radio speakers.
Uses of radio waves:
a) Radio and television communication
(to transmit sound and picture
information over long distance)
b) Radar & satellite communication
c) Navigation or ships & aircrafts
Uses of Radio Waves
TV and radio
Radio waves have the
wavelengths in the
These waves can be
longer than a
………………. or as short
as a …………….
Radio waves do more
than just bring music to
They also carry ………….
for your ……………… and