1. PRESENTATION
ON
MICROWAVE OVEN

3. CONTENTS
 Introduction
 Discovery
 Frequency range
 Microwave source
 Uses
 Frequency Bands
 Health Effects

4. INTRODUCTION
Microwaves are electromagnetic waves with wavelengths
ranging from 1 mm to 1 m, or frequencies between
300 MHz and 300 GHz. As a consequence, practical
microwave technique tends to move away from the discrete
resistors, capacitors, and inductors used with lower
frequency radio waves. Instead, distributed circuit elements
and transmission-line theory are more useful methods for
design, analysis. The term microwave generally refers to the
alternating current.
Electromagnetic waves longer (lower frequency) than
microwaves are called "radio waves". Electromagnetic
radiation with shorter wavelengths may be called
"millimeter waves", or t-rays

5. DISCOVERY
 The existence of electromagnetic waves, of which
microwaves are part of the frequency spectrum, was
predicted by James Clerk Maxwell in 1864 from his
equations . Heinrich Hertz was the first to demonstrate
the existence of electromagnetic waves by building an
apparatus that produced and detected microwaves in the
UHF region. J. C. Bose publicly demonstrated radio
control of a bell using millimeter wavelengths, and
conducted research into the propagation of microwaves.

6. FREQUENCY RANGES
 The microwave range
includes ultra-high frequency
(UHF) (0.3–3 GHz), super
high frequency (SHF) (3–
30 GHz), and extremely high
frequency (EHF) (30–
300 GHz) signals.
 Above 300 GHz, the
absorption of
electromagnetic radiation by
Earth's atmosphere is so
great that it is effectively
opaque, until the atmosphere
becomes transparent again in
the so-called infrared and
optical window frequency
ranges.

7. MICROWAVE SOURCE
 Vacuum tube based devices operate on the ballistic
motion of electrons in a vacuum under the influence of
controlling electric or magnetic fields, and include the
magnetron, klystron, travelling wave tube (TWT), and
gyrotron. These devices work in the density modulated
mode, rather than the current modulated mode. This
means that they work on the basis of clumps of electrons
flying ballistically through them, rather than using a
continuous stream.
A maser is a device similar to a laser, except that it
works at microwave frequencies.
Solid-state sources include the field-effect transistor, at
least at lower frequencies, tunnel diodes and Gunn
diodes.

8. GRAVITATIONAL WAVE SOURCE

9. USES
 COMMUNICATION
 REMOTE SENSING
 NAVIGATION
 POWER

10. COMMUNICATION
 Microwaves are used for communication, as they
are easier to control because small antennas could
direct these waves very easily.
 These waves can cover long distances very easily,
about 4 miles.
 Before the invention of optical fibers, microwaves
were used for communication., as they travel with
speed of light.
 Microwaves helps in wireless LAN protocol
Helps in MAN
 Cable TV and internet access on coaxial as well
as broadcast televisions uses microwave of lower
frequencies

11.  Mobile phones network and GSM also uses
microwaves of lower frequencies
 Microwave radio is used for broadcast and
telecommunication due to its high frequencies.
 Microwaves are used in television news to
transmit the signal from a remote location to a
television stations.
 Used for communication satellites.
 They are used for those areas where cables wire
could not be used

12. MICROWAVE LINK

13. A MICROWAVE TELECOMMUNICATION
TOWER

14. REMOTE SENSING
 Radar uses microwave radiation to detect the range,
speed, and other characteristics of remote objects. Now
radar is widely used for applications such as air traffic
control, navigation of ships, and speed limit
enforcement.
 A Gunn diode oscillator and waveguide are used as a
motion detector for automatic door openers.
 Most radio astronomy uses microwaves

15. RADAR SYSTEM

16. NAVIGATION
 Global Navigation Satellite Systems (GNSS)
including the American Global Positioning
System (GPS) and the Russian ГЛОбальная
НАвигационная Спутниковая Система
(GLONASS) broadcast navigational signals in
various bands between about is 1.2 GHz and 1.6
GHz.

17. NAVIGATION
NAVIGATION

18. POWER
 A microwave oven passes (non-ionizing)
microwave radiation (at a frequency near 2.45
GHz) through food, causing dielectric heating
by absorption of energy in the water, fats and
sugar contained in the food.
 Microwave heating is used in industrial
processes for drying and curing products.
 Many semiconductor processing techniques
use microwaves to generate plasma.

19.  Microwaves can be used to transmit power over
long distances. NASA worked in the 1970s and early
1980s to research the possibilities of using Solar
power satellite (SPS) systems with large solar arrays
that would beam power down to the Earth's surface
via microwaves.

20. A three-dimensional plot shows how the microwave frequency (x axis)
generated by a new NIST oscillator varies with changes in the current (y
axis). The height of each peak represents the power of the signal produced
at specific frequencies.

21. MICROWAVE FREQUENCY
BANDS
 The microwave spectrum is usually defined as
electromagnetic energy ranging from
approximately 1 GHz to 1000 GHz in
frequency, but older usage includes lower
frequencies. Most common applications are
within the 1 to 40 GHz range. Microwave
frequency bands, as defined by the Radio Society
of Great Britain (RSGB), are shown

22.  Microwave frequency bands
Designation Frequency range
 L band 1 to 2 GHz
 S band 2 to 4 GHz
 C band 4 to 8 GHz
 X band 8 to 12 GHz
 Ku band 12 to 18 GHz
 K band 18 to 26.5 GHz
 Ka band 26.5 to 40 GHz
 Q band 30 to 50 GHz
 U band 40 to 60 GHz
 V band 50 to 75 GHz
 E band 60 to 90 GHz

23.  W band 75 to 110 GHz
 F band 90 to 140 GHz
 D band 110 to 170 GHz (Hot)

24. Health effects
 Health effects of environmental
electromagnetic fields .
 Antibody responses of mice
exposed to low-power
microwaves .
 Cancer morbidity in subjects
occupationally exposed to high
frequency electromagnetic
radiation.
 Accelerated development of
spontaneous skin cancer in mice
exposed to 2350 MHz
microwave radiation.
 It is powerful and effects human
skin very badly.

26. CONTENTS
 INTRODUCTION
 PRINCIPLE
 INVENTION
 HOW IT WORKS
 EFFECTS OF MICROWAVE OVEN

27. INTRODUCTION
 A microwave oven, is a
kitchen appliance that can
come in many different sizes
and styles employing
microwave radiation
primarily to cook or heat
food. This is accomplished
by using microwaves, almost
always emitted from a
magnetron, to excite water
(primarily) and other
polarized molecules within
the food to be heated. This
excitation is fairly uniform,
leading to food being heated
everywhere all at once

28. Basic structure

29. PRINCIPLE
 Microwave oven works by passing non-ionizing microwave radiation,
usually at a frequency of 2.45 GHz (a wavelength of 12.24 cm), through the
food. Microwave radiation is between common radio and infrared
frequencies. Water, fat, and other substances in the food absorb energy
from the microwaves in a process called dielectric heating. Many molecules
(such as those of water) are electric dipoles, meaning that they have a
positive charge at one end and a negative charge at the other, and therefore
rotate as they try to align themselves with the alternating electric field of the
microwaves. This molecular movement creates heat as the rotating
molecules hit other molecules and put them into motion. Microwave
heating is most efficient on liquid water, and much less so on fats and
sugars (which have less molecular dipole moment), and frozen water (where
the molecules are not free to rotate). Microwave heating is sometimes
explained as a rotational resonance of water molecules, but this is incorrect:
such resonance only occurs in water vapor at much higher frequencies, at
about 20 gigahertz.

30. INVENTION
Cooking food with microwaves was discovered by
PERCY SPENCER while building magnetrons for radar
sets. He was working on an active radar set when he
noticed that a peanut chocolate bar he had in his pocket
started to melt. The radar had melted his chocolate bar
with microwave. Then he cooked popcorns and food in
microwave . Spencer created a high density
electromagnetic field by feeding microwave power into a
metal box which it had no way to escape. When food
was placed in the box with the microwave energy, the
temperature of the food rose rapidly.

31. WORKING
 Every microwave oven contains a magnetron, a
tube in which electrons are affected by magnetic and
electric fields in such a way to produce micro
wavelength radiation. This microwave radiation
interacts with the molecules in the food. All wave
energy changes polarity from positive to negative
with each cycle of the wave and this cause the polar
molecules to rotate at the same frequency millions of
times a second. All this agitation creates a molecular
friction within the food and at last this heats up the
food.

32. HARMFUL EFFECTS
 CANCER CAUSING EFFECTS
 DECREASE IN NUTRITIVE VALUES
 BIOLOGICAL EFFECTS

33. CANCER CAUSING EFFECTS
 CANCEROUS CELLS IN BLOOD
 TUMORS
 CREATION OF AGENTS
 ELEMENTAL FOOD
 UNSAFE FOR BABY’S MILK

34. DECREASE IN NUTRITIVE VALUES
DECREASE IN SOME TERMS OF
FOOD
 ENERGY CONTENTS
 NUCLEOPROTIENS

35. BIOLOGICAL EFFECTS
 DEGENERATION AND CIRCUIT
BREAKDOWNS.
 MICROWAVE SICKNESS.
 REPRODUCTIVE SYSTEM.
 HARMONES.