The waves theory

1. Electromagnetic
Waves & the
Electromagnetic
Spectrum
PREPARED BY: CHARLYN FAITH B. JUMAWAN

2. Learning Objectives:
Explain how an electromagnetic wave is
produced;
Compare the relative wavelength of the
different types of electromagnetic
waves;
Cite uses of Electromagnetic waves; and
Enumerate and explain the effects of
electromagnetic waves on humans and
the environment.

3. Values to be formed:
Show care and concern for one’s health
and environment
Exercise caution when dealing with
electromagnetic waves; and
Promote the use of wireless technology

4. Waves… a review
Most waves are either
longitudinal or transverse.
Sound waves are
longitudinal.
But all electromagnetic
waves are transverse…

5. ?
?

6. Electromagnetic
Waves
• Transverse waves without a medium!
• (They can travel through empty space)

9. • They travel as vibrations in electrical
and magnetic fields.
Have some magnetic and some electrical
properties to them.

10. When an electric field changes, so
does the magnetic field. The
changing magnetic field causes the
electric field to change. When one
field vibrates—so does the other.
 RESULT-An electromagnetic wave.

11. Electromagnetic waves travel VERY
FAST – around 300,000 kilometres
per second (the speed of light).
At this speed they can go around
the world 8 times in one second.

17.  Waves or Particles?
• Electromagnetic radiation has properties of waves but also can be thought
of as a stream of particles.
 Example: Light
 Light as a wave: Light behaves as a transverse wave which we can filter using polarized
lenses.
 Light as particles (photons): When directed at a substance light can knock electrons off
of a substance (Photoelectric effect)

18.  Electromagnetic Spectrum—name for the
range of electromagnetic waves when placed
in order of increasing frequency
RADIO
WAVES
MICROWAVES
INFRARED
RAYS
VISIBLE LIGHT
ULTRAVIOLET
RAYS
X-RAYS
GAMMA
RAYS

19. Notice the wavelength is
long (Radio waves) and gets shorter (Gamma Rays)

20. The Electromagnetic Spectrum
The EM spectrum is the ENTIRE range of EM waves in order
of increasing frequency and decreasing wavelength.
As you go from left  right, the wavelengths get smaller and the
frequencies get higher. This is an inverse relationship between wave
size and frequency. (As one goes up, the other goes down.) This is because the
speed of ALL EM waves is the speed of light (300,000 km/s).

22. What is the relationship between frequency and
wavelength?
INVERSE
(as one goes up, other goes down)

24. RADIO WAVES

26. Radio waves
Uses:
Automatic doors
Wi-Fi
Bluetooth
RFID (Radio Frequency
Identification) – similar to
Universal Product Code (UPC) or
bar code

28. Radio waves
 Uses:
 TV broadcasting
 AM and FM broadcast radio
 Heart rate monitors
 Cell phone communication
 Ideal for reducing the cellulite on the body, wrinkles, and fine lines on
the face, and for tightening sagging or loose skin.
 MRI (MAGNETIC RESONACE IMAGING)
 Uses Short wave radio waves with a magnet to create an image
 For viewing internal Parts of the human body without invasive surgery

29.  Global Positioning Systems (GPS) measure the time it takes a radio wave to
travel from several satellites to the receiver, determining the distance to
each satellite.

30.  Radar- an acronym for detection
and ranging. It makes use radio
waves for detection of objects,
weather forecasting, military
surveillance, and air craft control
as well as monitoring speed in
highway patrol and tracking
satellites and debris.

31. RADAR (Radio
Detection and
Ranging)
Used to find the
speed of an object
by sending out
radio waves and
measuring the
time it takes them
to return.

32.  A radio picks up radio waves through an
antenna and converts it to sound waves.
 Each radio station in an area broadcasts at a different frequency.
 # on radio dial tells frequency.

33. MRI
(MAGNETIC RESONACE IMAGING)
Uses Short wave radio waves with a
magnet to create an image.

35. MICROWAVES
Have the
shortest
wavelengths and
the highest
frequency of the
radio waves.

36. MICROWAVES
 USES
 are considered as HF radio waves and
are mainly used for communication.
Long distance telephone calls
To send signals for cable television
Video and audio feeds from production
vans to broadcast stations.
Remote sensing for disaster management
and mapping
Microwave doppler radars are used in
weather forecasting.

37. Used in microwave
ovens.
Waves transfer
energy to the
water in the food
causing them to
vibrate which in
turn transfers
energy in the form
of heat to the
food.

40. MICROWAVES
 Microwaves are highly used in the
medical field .
Microwave ablation – uses the heat
of the microwaves to shrink or
destroy tumors.
Microwave imaging – is used to
monitor the progress of treatment in
breast cancer, which can be
distinguished as benign or malignant
through microwave tomography.

41. INFRARED RAYS/RADIATION
 You can feel the
longest ones as
warmth on your
skin
Warm objects give
off more heat
energy than cool
objects.

42. Infrared Rays/Radiation
 Wavelengths in between
microwaves and visible light
 Uses:
Night vision goggles
Remote controls
Heat-seeking missiles

44.  You can feel the
longest ones as
warmth on your
skin
Warm objects give
off more heat
energy than cool
objects.

46. Thermogram—a picture that shows regions of different
temperatures in the body. Temperatures are calculated by
the amount of infrared radiation given off.
Therefore people give
off infrared rays.
Heat lamps give off
infrared waves.

49. VISIBLE LIGHT
 Shorter wavelength and
higher frequency than
infrared rays.
 Electromagnetic waves
we can see.
 Longest wavelength=
red light
 Shortest wavelength=
violet (purple) light

57. When light enters a new
medium it bends (refracts).
Each wavelength bends a
different amount allowing
white light to separate into
it’s various colors ROYGBIV.

58. ULTRAVIOLET RAYS
Shorter
wavelength and
higher frequency
than visible light
Carry more
energy than
visible light

62. Used to kill
bacteria.
(Sterilization
of equipment)

63. Too much can cause skin cancer.
Use sun block to protect against
(UV rays)

64. Causes your
skin to
produce
vitamin D
(good for
teeth and
bones)

66. X- RAYS
Shorter
wavelength and
higher frequency
than UV-rays
Carry a great
amount of
energy
Can penetrate
most matter.

69. Bones and teeth absorb x-rays. (The light part of an x-ray image indicates a
place where the x-ray was absorbed)

71. GAMMA RAYS
Shorter wavelength
and higher frequency
than X-rays
Carry the greatest
amount of energy and
penetrate the most.

74. Too much exposure
can cause cancer
(lead vest at
dentist protects
organs from
unnecessary
exposure)

75.  Used by engineers to check
for tiny cracks in structures.
 The rays pass through the
cracks and the cracks
appear dark on film.

76. Used in radiation treatment to kill
cancer cells.
Can be very harmful if not used
correctly.

77. The Incredible
Hulk was the
victim of
gamma
radiation.

78. Exploding nuclear
weapons emit
gamma rays.

79. Brief SUMMARY
 A. All electromagnetic waves travel at the same speed. (300,000,000
meters/second) in a vacuum.
 B. They all have different wavelengths and different frequencies.
 Long wavelength-lowest frequency
 Short wavelength highest frequency
 The higher the frequency the higher the energy.

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