3. Objectives:
a. Cite examples of practical applications
of the different regions of EM waves,
such as the use of radio waves in
telecommunications. (S10-FE-Iic-d-48)
b. Discuss the practical uses of EM waves
c. Describe how EM waves can be used in
daily activities.
5. • They travel as vibrations in
electrical and magnetic fields.
– Have some magnetic and some
electrical properties to them.
6. 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.
7. 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.
9. RADIO WAVES
Have the longest
wavelengths
and lowest
frequencies of
all the
electromagneti
c waves.
10. 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.
11. 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.
12. • Audio – frequency (AF) signals – patterns
of electric current variations.
• Radio – frequency (RF) – high frequency
radio waves.
• Frequency Modulation – frequency of a
wave that changes to match that of a
signal.
15. 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.
APPLICATIONS OF MICROWAVE
16. RADAR (Radio Detection and Ranging)
• A radar system is
consisting of an
antenna, transmitter
and a receiver.
• Electromagnetic sensor
used for detecting,
locating, tracking, and
recognizing objects of
various kinds at
considerable distances.
19. 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.
20. Blue and green indicate regions of cooler
temperature.
Red and yellow indicate warmer
temperature
21. Applications of Infrared
1. Infrared Photographs – provides useful
details of the vegetation of the Earth’s
surface.
26. VISIBLE LIGHT
Shorter wavelength and higher frequency
than infrared rays.
Electromagnetic waves we can see.
Longest wavelength= red light
Shortest wavelength= violet (purple) light
27. 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.
29. Some Uses of UV Radiation
• Sun is the main source of ultraviolet
radiation but there are also artificial
sources of UV light.
1. UV lamps are used by banks to check the
signature on a passbook.
30. Some Uses of UV Radiation
2. UV radiation is also used in sterilizing
water from drinking fountains.
31. Some Uses of UV Radiation
3. UV radiation in sunlight produces
Vitamin D in the skin and gives us
tanning effect.
39. Bones and teeth absorb
x-rays. (The light part
of an x-ray image
indicates a place where
the x-ray was absorbed)
Long Wavelength X-rays
40. Too much exposure can
cause cancer
(lead vest at dentist
protects organs
from unnecessary
exposure)
41. Short Wavelength X-rays
Used by engineers to
check for tiny cracks
in structures.
– The rays pass
through the cracks
and the cracks
appear dark on film.
46. 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.
