Microwave oven

PRESENTATION

ON

MICROWAVE OVEN

CONTENTSCONTENTS

IntroductionIntroduction DiscoveryDiscovery Frequency rangeFrequency range Microwave sourceMicrowave source UsesUses Frequency BandsFrequency Bands Health EffectsHealth Effects

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

INTRODUCTIONINTRODUCTION

DISCOVERYDISCOVERY

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

FREQUENCY RANGESFREQUENCY RANGES The microwave range The microwave range

includes ultra-high frequency includes ultra-high frequency (UHF) (0.3–3 GHz), super (UHF) (0.3–3 GHz), super high frequency (SHF) (3–high frequency (SHF) (3–30 GHz), and extremely high 30 GHz), and extremely high frequency (EHF) (30–frequency (EHF) (30–300 GHz) signals.300 GHz) signals.

Above 300 GHz, the Above 300 GHz, the absorption of absorption of electromagnetic radiation by electromagnetic radiation by Earth's atmosphere is so Earth's atmosphere is so great that it is effectively great that it is effectively opaque, until the atmosphere opaque, until the atmosphere becomes transparent again becomes transparent again in the so-called infrared and in the so-called infrared and optical window frequency optical window frequency ranges.ranges.

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

GRAVITATIONAL WAVE GRAVITATIONAL WAVE SOURCESOURCE

USESUSES

COMMUNICATIONCOMMUNICATION REMOTE SENSINGREMOTE SENSING NAVIGATIONNAVIGATION POWERPOWER

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

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

MICROWAVE LINK MICROWAVE LINK

A MICROWAVE TELECOMMUNICATION A MICROWAVE TELECOMMUNICATION TOWERTOWER

REMOTE SENSINGREMOTE SENSING Radar uses microwave radiation to detect Radar uses microwave radiation to detect

the range, speed, and other the range, speed, and other characteristics of remote objects. Now characteristics of remote objects. Now radar is widely used for applications such radar is widely used for applications such as air traffic control, navigation of ships, as air traffic control, navigation of ships, and speed limit enforcement.and speed limit enforcement.

A Gunn diode oscillator and waveguide A Gunn diode oscillator and waveguide are used as a motion detector for are used as a motion detector for automatic door openers.automatic door openers.

Most radio astronomy uses microwavesMost radio astronomy uses microwaves

RADAR SYSTEMRADAR SYSTEM

NAVIGATIONNAVIGATION

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

NAVIGATIONNAVIGATIONNAVIGATION

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

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

A three-dimensional plot shows how the microwave A three-dimensional plot shows how the microwave frequency (x axis) generated by a new NIST oscillator frequency (x axis) generated by a new NIST oscillator varies with changes in the current (y axis). The height varies with changes in the current (y axis). The height

of each peak represents the power of the signal of each peak represents the power of the signal produced at specific frequencies.produced at specific frequencies.

MICROWAVE FREQUENCY MICROWAVE FREQUENCY BANDSBANDS

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

Microwave frequency bandsMicrowave frequency bandsDesignationDesignationFrequency rangeFrequency range L bandL band 1 to 2 GHz1 to 2 GHz S bandS band 2 to 4 GHz2 to 4 GHz C bandC band 4 to 8 GHz4 to 8 GHz X bandX band 8 to 12 GHz8 to 12 GHz Ku bandKu band 12 to 18 GHz12 to 18 GHz K bandK band 18 to 26.5 GHz18 to 26.5 GHz Ka bandKa band 26.5 to 40 GHz26.5 to 40 GHz Q bandQ band 30 to 50 GHz30 to 50 GHz U bandU band 40 to 60 GHz40 to 60 GHz V bandV band 50 to 75 GHz50 to 75 GHz E bandE band 60 to 90 GHz60 to 90 GHz

W bandW band 75 to 110 GHz75 to 110 GHz F bandF band 90 to 140 GHz90 to 140 GHz D bandD band 110 to 170 GHz (Hot)110 to 170 GHz (Hot)

Health effectsHealth effects Health effects of Health effects of

environmental environmental electromagnetic fields .electromagnetic fields .

Antibody responses of Antibody responses of mice exposed to low-power mice exposed to low-power microwaves .microwaves .

Cancer morbidity in Cancer morbidity in subjects occupationally subjects occupationally exposed to high frequency exposed to high frequency electromagnetic radiation. electromagnetic radiation.

Accelerated development Accelerated development of spontaneous skin cancer of spontaneous skin cancer in mice exposed to 2350 in mice exposed to 2350 MHz microwave radiation. MHz microwave radiation.

It is powerful and effects It is powerful and effects human skin very badly.human skin very badly.

CONTENTSCONTENTS

INTRODUCTIONINTRODUCTION PRINCIPLEPRINCIPLE INVENTIONINVENTION HOW IT WORKSHOW IT WORKS EFFECTS OF MICROWAVE OVENEFFECTS OF MICROWAVE OVEN

INTRODUCTIONINTRODUCTION A A microwave ovenmicrowave oven, is a , is a

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

Basic structureBasic structure

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

INVENTIONINVENTION

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.

WORKINGWORKING

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

HARMFUL EFFECTSHARMFUL EFFECTS

CANCER CAUSING EFFECTSCANCER CAUSING EFFECTS

DECREASE IN NUTRITIVE DECREASE IN NUTRITIVE VALUESVALUES

BIOLOGICAL EFFECTSBIOLOGICAL EFFECTS

CANCER CAUSING EFFECTSCANCER CAUSING EFFECTS

CANCEROUS CELLS IN CANCEROUS CELLS IN BLOODBLOOD

TUMORSTUMORS

CREATION OF AGENTSCREATION OF AGENTS

ELEMENTAL FOODELEMENTAL FOOD

UNSAFE FOR BABY’S MILKUNSAFE FOR BABY’S MILK

DECREASE IN NUTRITIVE VALUESDECREASE IN NUTRITIVE VALUES

DECREASE IN SOME TERMS OF DECREASE IN SOME TERMS OF FOODFOOD

ENERGY CONTENTSENERGY CONTENTS

NUCLEOPROTIENSNUCLEOPROTIENS

BIOLOGICAL EFFECTSBIOLOGICAL EFFECTS

DEGENERATION AND CIRCUIT DEGENERATION AND CIRCUIT BREAKDOWNS.BREAKDOWNS.

MICROWAVE SICKNESS.MICROWAVE SICKNESS.

REPRODUCTIVE SYSTEM.REPRODUCTIVE SYSTEM.

HARMONES.HARMONES.