electromagnetic spectrum & its uses

1. ELECTROMAGNETIC
WAVES AND THE
ELECTROMAGNETIC
SPECTRUM

2. Electromagnetic Radiation
 Electromagnetic waves perpendicular
waves combing the electric and magnetic
fields.
 Electromagnetic waves are produced when
an electric charge vibrates or accelerates
and can travel through empty space or
through matter.

3. Electromagnetic Spectrum
 Gamma rays
 X – rays
 Ultraviolet
 Visible light
 Infra-red
 Microwaves
 Radio waves
Highest frequency
Shortest wavelength
Lowest frequency
Longest wavelength

4. Electromagnetic Spectrum
Diagram
 Diagram of Electromagnetic Spectrum
(including the relationship between frequency
and wavelength).

5. 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
decreases.

6. Electromagnetic Spectrum
 Includes the following types of waves
 Radio
 Microwaves
 Radar
 Infrared
 Visible Light
 Ultraviolet
 X-Rays
 Gamma Rays

7. Electromagnetic Spectrum
 ………………………………………………

8. Hence this is the complete EM wave spectrum (the waves below in
 ascending order of wavelength;
descending order of frequency )
Gamma
rays
x-rays Ultra-violet
ray
Visible
light
Infra-
red ray
Microwave Radio wave
Highest f
Shortest λ
Lowest f
Longest λ

9. Waves
Longitudinal Waves Transverse Waves
Electromagnetic Waves
Properties
Electromagnetic Spectrum
Radiowave
Microwave
Infra-Red
Light
Ultra-Violet
X-ray
Gamma ray
Sound waves
Classified into
Comprises of
Overview of EM waves

10. Gamma rays
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
treatment.

11. Uses of Gamma Rays
 Kill cancer cells
 Study the nucleus
in atoms

12. Gamma Rays
 Gamma rays are the highest
energy electromagnetic wave.
 They usually come from
radioactive elements or stars
 Uses include:
 Killing cancer cells
 Making pictures of the brain
 Inspection tools in industry

13. X-rays
X rays is generated by :
a) Rapid deleceration of fast moving
electrons
b) Changes in energy of innermost orbital
electrons
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
the body.
• 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.

14. X-Rays
 X-Rays have high energy and can penetrate
some material.
 Used in:
 Medicine
 Industry
 Transportation
 Too much exposure can damage
living tissue or even cause cancer.

15. X - Rays
 X-Ray radiation has a high
…………………….. ability and
can pass right through our
bodies.
 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
X-rays.
 Over exposure can cause
……….. …………………….

16. Uses of X-rays
 Take ‘pictures’ of
bones in the body
 Study the crystal
structure of crystalline
substances
 Check for cracks in
metal plates

17. Ultraviolet Waves
 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

18. Ultra-violet
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
c) Fluorescence

19. Uses of Ultraviolet
 Detect counterfeit
notes
 Gives the clothes a
‘glow’ effect in
discotheques
 Sun-tanning
 Sterilise medical
equipment

20. Visible Light
 Visible light is made up of the various ..................... of
colored light.
 The ……… is determined by the frequency of the light.
 When electromagnetic radiation of this frequency falls
on our ……………. our brain interprets it as colour.

21. Visible Light
Visible light is the part of the EM
spectrum which can be detected by the
human eye.
The visible light has its own spectrum
which consist of the 7 colours of light :
Red Orange Yellow Green Blue Indigo
Violet
An example of visible light is the
colourful laser light or the light from a
firework.
Some of the uses of light is in
optical fibres in medicine and
telecommunications.

22. Visible Light
 Our eyes detect
electromagnetic energy in a
small portion of the
electromagnetic spectrum
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.

23. Uses of Visible Light
 Enable us to see
things
 Photosynthesis in
plants

24. Infra-red waves
Heat can be transferred through infrared
radiation.
We often think of infra red as being the same
thing as 'heat', because it makes our skin feel
warm.
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
injuries

25. Uses of Infra-red
 Heating
 Haze photography

26. Infrared image of a human body. Red is hot, blue is cool.

27. Infrared Waves
 Infrared waves are heat waves.
 All objects emit infrared waves because all objects
possess heat.
 Night vision goggles detect infrared waves and allow
the user to see the movement of objects in the dark.
 Many TV remotes use infrared.

28. Microwaves
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
atomic structure
c) Useful demonstration of all wave
properties on macroscopic scale
d) Telephone communication (mobile
phones, etc)

29. Uses of Microwaves
 Radar
communication
 Analysis of the
molecular and
atomic structure
 Telephone
communications

30. Radio waves
Radio waves are the electromagnetic waves
with the longest wavelengths and lowest
frequencies
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

31. Uses of Radio Waves
 Radar
communications
 TV and radio
broadcasting

32. Radio Waves
 Radio waves have the
…………………
wavelengths in the
electromagnetic spectrum.
 These waves can be
longer than a
………………. or as short
as a …………….
 Radio waves do more
than just bring music to
your radio.
 They also carry ………….
for your ……………… and
………………….. phones

33.  THANK YOU ……..