Electromagnetic spectrum & laws of radiation and its application in physiotherapy

Electromagnetic
Spectrum
- Dr. Rushikesh K. Joshi
MPT Neurology &
Psychosomatic Disorders

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

What are Electromagnetic
Waves ?
• Definition-
‘Distribution of the continuum of all radiant
energies can be plotted either as a function of
wavelength or of frequency in a chart known as
the electromagnetic spectrum”
• If you have ever tuned in to listen to a radio,
spoken on a handphone, turned on a light, had
an X-ray taken, felt the warmth of sun on your
skin.
• You have experienced electromagnetic waves
Dr. Rushikesh Joshi, PT (MPT
Neurology)

Electromagnetic wave
Produced by Simultaneous vibration
Electric field
Magnetic field
Electric field
Magnetic field
Neurology)

Wavelength of Electromagnetic Waves
Neurology)

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
Neurology)

Properties of EM Wave
1. All electromagnetic waves are transverse
wave
Neurology)

2. They do not require any medium to travel
through (recall: Radiation Infra red is an EM Wave)
3. They travel at the speed of 3x108 ms-1 in
vacuum (recall: speed of light  light is also an EM Wave)
Neurology)

4. They can all be reflected or refracted
Neurology)

5. They can all be emitted or absorbed by
matter
Neurology)

6. They all obey the wave equation
Where v = speed of wave (m/s)
f = frequency of wave (Hz)
λ = wavelength (m)
v =f x λ
Neurology)

7. Their frequencies do not change as
they pass from one medium to
another. However, both their speed
and wavelength will change.
v =f x λ
Neurology)

9. They are all of
neutral charge as all
of them oscillate
with electric and
magnetic field
perpendicular to
each other.
8. They carry energy from one place to
another
Neurology)

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.
Neurology)

X-rays
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.
.
Neurology)

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.
Neurology)

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
.
Neurology)

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.
Infra red is useful for:
-
- Medical treatment : to warm injured
muscles/sports injuries
Neurology)

Microwaves
One of their most common
uses is in microwave ovens.
Other uses of microwaves:
• Radar communication (as it
is not easily blocked of by
buildings/trees)
• Telephone communication
(mobile phones, etc)
Neurology)

Radio waves
Radio waves are the electromagnetic
waves with the longest
wavelengths and lowest
frequencies
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
Neurology)

Some tips to help you to remember:
• EM Spectrum (increasing wavelength)
Raja’s Mother Is Visiting Uncle Xavier’s Garden
• Visible Light Spectrum
Run Off You Girls Boys In View
Radio
wave
Micro
wave
Infra-red
Rays
Visible
light
Ultra-violet
ray
X-rays Gamma
rays
red orange yellow green blue indigo violet
Neurology)

Laws of Radiations
/ Laws of Emission
Neurology)

Law of Reflection
• Reflection is a process which occurs when
an electromagnetic wave encounters a
medium, which will not transmit it.
• In this case, the incident ray will be
reflected back in the same plane.
• The angle between the incident ray and
reflected ray will be the same..
Neurology)

Neurology)

Application
• Laws of reflection are used in designing of
the reflectors used for the redirection of
rays towards the appropriate target.
• Infrared and ultraviolet lamps used in
physiotherapy used the reflectors.
• This are known as parabolic reflectors.
• it avoids the danger of concentration of
rays.
Neurology)

Law of refraction
• Refraction occurs when EM rays are
transmitted from one medium to another
medium, with an angel of incidence
greater than zero.
• Rays with zero angle of incidence will go
straight through the transmitting medium.
Neurology)

Application
• Useful in hydrotherapy and ultrasound
therapy in which water is used as medium
of treatment. The refraction of rays
passing from water to air makes the
position of objects in water difficult to
assess.
Neurology)

Absorption
• When EM rays strike a new medium, they
may be absorbed and thus produce an
effect.
• Law of grothus-
– The rays may be absorbed on surface to
produce the effect.
– The proportion of the rays absorbed depends
upon the wavelength of the rays, nature of
medium and the angle of incidence.
Neurology)

• Lambert’s cosine law-
– It tells that the intensity of the rays at surface
varies with the cosine of the angle between
the incident ray and the normal.
– APPLICATION-
Therefore while applying ultraviolet and
infrared rays, greater effort should be made to
ensure that the maximum number of rays
strike the surface at 90 degree for most
effective treatment..
Neurology)

Inverse square law
• When EM waves are produced from a
point source obey inverse square law.
• This states that the intensity of rays from a
point source varies inversely with the
sqauare of the distance from that source.
• Rays produced from a point source
diverge from one another.
Neurology)

Application
• Ultraviolet lamp or IRR lamp act as a point
source, the rays generated obey the
inverse square law.
• So, closer the patients is to the source, the
greater is the intensity of the radiation
being received.
Neurology)

Electromagnetic spectrum & laws of radiation and its application in physiotherapy

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Electromagnetic spectrum & laws of radiation and its application in physiotherapy

Similar to Electromagnetic spectrum & laws of radiation and its application in physiotherapy (20)

More from Dr. Rushikesh K. Joshi, PT

More from Dr. Rushikesh K. Joshi, PT (12)

Recently uploaded

Recently uploaded (20)

Electromagnetic spectrum & laws of radiation and its application in physiotherapy