SCIENCE 10 LESSON

3. Electromagnetic Waves
• If you have ever tuned in to
listen to a radio ,a spoken
headphone , turned on a light
,hand on X ray taken, felt the
warmth of the sun on your
skin.
• You have experienced
ELECTROMAGNETIC WAVE.

4. Definition
• “Electromagnetic waves are waves
which can travel through the
vacuum of outer space .
• Electromagnetic waves are formed
when an electric field couples with
a magnetic field.
• The magnetic and electric fields of
an electromagnetic waves are
perpendicular to each other and to
the direction of waves.”

5. How do moving charges create
magnetic fields?
• Any moving electric charge is surrounded by an
electric field and a magnetic field.

6. Production of
Electromagnetic Waves
• When an electric charge vibrates,
the electric field around it changes
creating a changing magnetic field.

7. • The magnetic and electric fields create
each other again and again.

8. • An EM wave travels in all directions.
The figure only shows a wave traveling
in one direction.

9. • The electric and magnetic fields vibrate
at right angles to the direction the wave
travels so it is a transverse wave

10. What is the speed of EM waves?
• All EM waves travel 300,000
km/sec in space. (speed of
light-nature’s limit!)
• EM waves usually travel slowest
in solids and fastest in gases.

11. Properties of electromagnetic
wave
1. All are electromagnetic waves are
transverse
2. They do not required any medium to
travel though .
3. They travel at speed of 3 multiple by
10 -8 in vacuum.
4. They can all be reflected and refracted.
5. They can all be emitted and absorb by
matter.

12. Graphically Representation

13. Electro Spectrum
“Frequencies is called the
electromagnetic spectrum.”
• Different parts interacts with matter in
different way
• As wavelength decreases, frequency
increases…
• The ones humans can see are called visible
light, a small part of the whole spectrum.

14. Chart of wave length and
frequency

15. Electromagnetic spectrum
• Includes following types of waves :
• Radio waves
• Microwaves
• Infrared waves
• Visible light
• Ultraviolet
• X rays
• Gamma rays

17. Region Frequency Wavelength Energy
Radio waves < 109
> 0.3 < 7x 10-7
Microwaves 109 - 3x1011
0.001 - 0.3
7x10-7 - 2x10-
4
Infrared 3x1011 -
3.9x1014
7.6x10-7 -
0.001
2x10-4 - 0.3
Visible 3.9x1014 -
7.9x1014
3.8x10-7 -
7.6x10-7 0.3 - 0.5
Ultraviolet 7.9x1014 -
3.4x1016
8x10-9 -
3.8x10-7
0.5 - 20
X-rays 3.4x1016 -
5x1019
6x10-12
- 8x10-9
20 - 3x10 4
Gamma rays > 5x1019 < 6x10-12 > 3x104

18. Radio waves
• Radio waves have the longest
wavelengths of all the
electromagnetic waves.
• Low frequency.
• Radio waves are often used to
transmit data and have been used
for all sorts of applications
including radio, satellites, radar,
and computer networks.

19. Radio waves are used in
medicine
• Is used to produce images of soft
tissues, fluid, fat and bone.
Example : MRI and RFA.
• DIAGNOSE MANY PROBLEMS.
Example : helps identify tumors.
• Radiofrequency Ablation (RFA)
uses heat to destroy cancer cells.

20. • Microwaves are radio waves
with wavelengths less than 30
cm and higher frequency &
shorter wavelength
• Cell phones and satellites use
microwaves between 1 cm & 20
cm for communication

21. • Microwaves are useful in
communication because they
can penetrate clouds, smoke,
and light rain.
• Microwave also in radar that
helps to predict the weather.

22. Microwave waves are used in
medicine
• Hyperthermia therapy is a type of
medical treatment.
• Microwave ablation: used in
treatment of liver tumor
• Microwave diathermy: used in pain
management
• Transurethral microwave :
thermotherapy used in treatment of
lower urinary tract syndrome

23. Infrared waves:
• Infrared waves are sometimes
classified as "near" infrared or
"far" infrared
• Between microwaves and visible
light are infrared waves.
• Can be detected by heat and used in
heat lamp.
• Higher energy then microwave and
lower the visible light.
• Used daily in remote controls, to
read CD-ROMs

24. Precautions
• Strong infrared radiation in
certain industry high-heat
settings may be hazard to
the eyes, resulting in damage
or blindness to the user.
• Since the radiation is
invisible, special IR-proof
goggles must be worn in such
places

25. Modalities use
• Infrared lamps
• Digital infrared camera

26. Infrared Imaging in Medicine
• Oncology
• Vascular disorders
• Respiratory disorders
• Skeletal
• neuromuscular diseases
• Surgery
• Tissue viability

27. Visible light
• This is the range of
wavelengths from 390 to 700
nm which corresponds to the
frequencies 430-790 THz.
• The portion of the
electromagnetic spectrum
that human eyes can detect.

28. You see different wavelengths
as colors.
Blue has shortest
Red is the longest
Light looks white if all
colors are present

29. Visible light use in medicines
• Visible light is also used
in Scanning laser
ophthalmoscope.
• In Endoscopy/ Keyhole
Surgery

30. Ultraviolet Waves
• Ultraviolet waves have the next
shortest wavelength after visible
light.
• EM waves with wavelengths from
about 400 billionths to 10
billionths of a meter.
• Used in tanning beds and
sterilizing equipments.

31. Ultraviolet Waves use in medicines
• Have enough energy to enter
skin cells
• Longer wavelengths – UVA
• Shorter wavelengths – UVB
rays
• Both can cause skin cancer

32. • Ultraviolet light is used in
treatment of Psoriasis and
Vitiligo
• Pregnancy
• Abnormalities in the heart and
blood vessels
• Organs in the pelvis and
abdomen
• Symptoms of pain, swelling and
infection

33. Can UV radiation be useful
• Helps body make vitamin D for
healthy bones and teeth
• Used to sterilize medical supplies &
equip
• Detectives use fluorescent powder
(absorbs UV & glows) to find
fingerprints

34. X Rays
• High wave energy
• Used in :
Medicines
Industry
Transportation
• To much exposure can
damage the living tissue or
even cause cancer

35. • X-rays play an important role in
dentistry and orthopedic
investigation.
• They can penetrate soft tissue
like skin and muscle.
• Are used to take X-ray pictures
of bones in medicine.

36. • Gamma rays the highest
energy electromagnetic
waves
• The actually come from
radioactive elements or
stars
• Inspection tools in industry

37. Positron Emission Tomography
(PET) is a nuclear medical
imaging tool which used
gamma rays.
• Example :
• Neurological diseases such as
Alzheimer’s and Multiple
Sclerosis
• Effectiveness of treatments

38. • Heart conditions
• Gamma Knife uses beams of
highly focused gamma rays to
treat tumors or other
abnormalities in the brain.
• Gamma rays can check how
far a cancer has spread and
how well treatment is working.