PRESENTATION ON MICROWAVE OVEN

CONTENTS Introduction Introduction Discovery Discovery Frequency range Frequency range Microwave source Microwave source Uses Uses Frequency Bands Frequency Bands Health Effects Health Effects

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 INTRODUCTION

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. 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.James Clerk Maxwell equationsHeinrich HertzJ. C. BoseJames Clerk Maxwell equationsHeinrich HertzJ. C. Bose

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. 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. 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.

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.

GRAVITATIONAL WAVE SOURCE

USES COMMUNICATION COMMUNICATION REMOTE SENSING REMOTE SENSING NAVIGATION NAVIGATION POWER POWER

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

 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

MICROWAVE LINK

A MICROWAVE TELECOMMUNICATION TOWER

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. 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. A Gunn diode oscillator and waveguide are used as a motion detector for automatic door openers. Most radio astronomy uses microwaves Most radio astronomy uses microwaves

RADAR SYSTEM

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. 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.

NAVIGATION NAVIGATION

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.

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. 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.

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.

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 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

Microwave frequency bands Microwave frequency bands DesignationFrequency range L band1 to 2 GHz L band1 to 2 GHz S band2 to 4 GHz S band2 to 4 GHz C band4 to 8 GHz C band4 to 8 GHz X band8 to 12 GHz X band8 to 12 GHz Ku band12 to 18 GHz Ku band12 to 18 GHz K band18 to 26.5 GHz K band18 to 26.5 GHz Ka band26.5 to 40 GHz Ka band26.5 to 40 GHz Q band30 to 50 GHz Q band30 to 50 GHz U band40 to 60 GHz U band40 to 60 GHz V band50 to 75 GHz V band50 to 75 GHz E band60 to 90 GHz E band60 to 90 GHz

W band75 to 110 GHz W band75 to 110 GHz F band90 to 140 GHz F band90 to 140 GHz D band110 to 170 GHz (Hot) D band110 to 170 GHz (Hot)

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

CONTENTS INTRODUCTION INTRODUCTION PRINCIPLE PRINCIPLE INVENTION INVENTION HOW IT WORKS HOW IT WORKS EFFECTS OF MICROWAVE OVEN EFFECTS OF MICROWAVE OVEN

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 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 kitchenappliance microwave radiationcook food magnetronwater polarized molecules kitchenappliance microwave radiationcook food magnetronwater polarized molecules

Basic structure

PRINCIPLE Microwave oven works by passing non-ionizing microwave radiation, usually at a frequency of 2.45 GHz (a wavelength of 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. Microwave oven works by passing non-ionizing microwave radiation, usually at a frequency of 2.45 GHz (a wavelength of 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.

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.

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. 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.

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

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

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

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