Microwaves -presentation- DR INZ. ZDZISŁAW PÓLKOWSKI Polkowice-2015 University of Pitesti and Dolnośląska Wyższa Szkoła Przedsiębiorczości i Techniki w Polkowicach STUDENT: CONSTANTIN IONUT
Content presentation 1) Microwaves-presentation 2) Content presentation 3) Inventor of the Microwave 4) Microwave-definition 5) How Microwave Cooking Works 6) Advantages of Microwaves 7) Disadvantages of Microwave 8) Applications of Microwaves 9) Microwaves of Radiofrequency Radiation 10) End of the presentation
Inventor of the Microwave The man was Percy Spencer. At the age of just 18 months old, Spencer’s father died and his mother soon left him to his aunt and uncle. His uncle then died when Spencer was just seven years old. Spencer subsequently left grammar school and, at the age of 12, began working from sunup to sundown at a spool mill, which he continued to do until he was 16 years old. At this time, he heard about a nearby paper mill that was “electrifying”, which intrigued him. Given that few in his town, a remote community in Maine, knew much of anything about electricity, he began learning what he could about it and managed to become one of three people who were hired to install electricity in the plant, despite having never received any formal training in electrical engineering nor even finishing grammar school.
Microwave Microwave -definition- The term microwave refers to electromagnetic energy having a frequency higher than 1 gigahertz (billions of cycles per second), corresponding to wavelength shorter than 30 centimeters. Microwave signals propagate in straight lines and are affected very little by the troposphere. They are not refracted or reflected by ionized regions in the upper atmosphere. Microwave beams do not readily diffract around barriers such as hills, mountains, and large human-made structures. Some attenuation occurs when microwave energy passes through trees and frame houses. Radio-frequency (RF) energy at longer wavelengths is affected to a lesser degree by such obstacles. The microwave band is well suited for wireless transmission of signals having large bandwidth. This portion of the RF electromagnetic radiation spectrum encompasses many thousands of megahertz. In communications, a large allowable bandwidth translates into high data speed.
How Microwave Cooking Works Not surprisingly, a microwave oven uses microwaves to heat food. Microwaves are a type of wave that are sandwiched between radio waves and infrared radiation on the electromagnetic spectrum. In the case of microwave ovens, the commonly used wave frequency is roughly 2,450 megahertz (2.45 gigahertz). Waves in this frequency range have an interesting property: They're absorbed by water, fats and sugars. Once absorbed, they're converted directly into atomic motion-heat. These waves boast another interesting, related property, too: They're not absorbed by most plastics, glass or ceramics. Metal reflects microwaves, which is why metal pans don't work well in a microwave oven.
Advantages of Microwaves Large Bandwidth: The Bandwidth of Microwaves is larger than the common low frequency radio waves. It is very good advantage, because of this, Microwaves are used for Point to Point Communications. Better Directivity: At Microwave Frequencies, there are better directive properties. This is due to the relation that As Frequency Increases, Wavelength decreases and as Wavelength decreases Directivity Increases and Beam width decreases. So it is easier to design and fabricate high gain antenna in Microwaves. Small Size Antenna: Microwaves allows to decrease the size of antenna. Thus in Microwaves, we have waves of much higher frequencies and hence the higher the frequency, the smaller the size of antenna. Low Power Consumption: The power required to transmit a high frequency signal is lesser than the power required in transmission of low frequency signals. As Microwaves have high frequency thus requires very less power.
Disadvantages of Microwave Loss of Nutrients: A study at Osaka Prefecture University in 1998 showed that cooking pork, beef and milk in a microwave oven lowered the amount of vitamin B12 by 30 to 40 percent. A study by Cornell University showed that microwaving spinach reduced the nutrient folate by a negligible amount compared to cooking it on the stove (77 percent loss). These studies show that microwaves can reduce nutritional content but not necessarily more or less than other methods of cooking. Theories on Negative Effects: In the 1970s in Russia, the microwave was banned after a post World War II report that stated microwaves led to many possible health problems. Natural health practitioners who believe the microwave is dangerous point to this study and speculate that the device can lead to increased disease and a stronger chance of cancer.
Applications of Microwaves There are many Industrial, Scientific, Medical and Domestic Applications of Microwaves: Communication: Microwave is used in broadcasting and telecommunication transmissions. Microwaves are also used for transmitting and receiving a signal from earth to satellite and from satellite to earth. Military or Army also makes use of Microwaves in their communication system. They uses X or Ku band for their communication. Remote Sensing: The most common application of Microwave is its use in RADAR and SONAR. RADAR is used to illuminate an object by using a transmitter and receiver to detect its position and velocity. Heating: We uses Microwave Oven to bake and cook food. It is very convenient electronic machine which performs the heating task very cleanly and in a very less time. Medical Science: Microwave's heating properties are also used in Medical Science and in diagnosis and therapies.
Microwaves of Radiofrequency Radiation Radiation is the emission (sending out) of energy from any source. X-rays are an example of radiation. When talking about radiation and cancer, many people think of specific kinds of radiation such as x-rays or the radiation made by nuclear reactors. But there are other types of radiation that act differently. Radiation exists across a spectrum from very high-energy (high- frequency) radiation to very low-energy (low-frequency) radiation. Examples of high-energy radiation include x-rays and gamma rays. They, as well as some higher energy UV radiation, are called ionizing radiation, which means they have enough energy to remove an electron from (ionize) an atom or molecule. This can damage the DNA inside of cells, which can result in cancer. If RF radiation is absorbed in large enough amounts by materials containing water, such as food, fluids, and body tissues, it can produce heat.
End of the presentation