"Magnetic Resonance Imaging is used in for medical imaging. The procedure for an MRI is the following. Unlike an X ray examination or CT scan MRI does not depend on ionizing radiation. Instead while in the magnet, radio waves redirect the axes of spinning protons. The magnetic field is produced when electric currents are passed through wire coils. Other coils as side from these coils, located in the machine which are plased around the body being imaged recieves and sends radio waves. They then produce signals. A computer picks up these signals and generates a series of images. Thus the image can be studied. This is the basic sturture of how an MRI works. During the examination people must be still and some times asked to hold their breath by the docter. This is all procedures to can an accurate MRI."
How Magnetic Resonance Imaging Works
(Nuclear magnetic resonance imaging provides safe nonintrusive medical diagnostic images of the interior of the human body. How does MRI work?)
One of the many modern diagnostic tools available to medical doctors is magnetic resonance imaging (MRI). MRI scans provide physicians a view of the interior of the patient's body without harming or invading the patient's body in any way. Magnetic resonance imaging is based on the fundamental physics of nuclear magnetic resonance (NMR). How does MRI work?
Nuclear Magnetic Resonance
Nuclear magnetic resonance is an effect that occurs when the nucleus of an atom is placed in a magnetic field. The spinning nucleus in a constant magnetic field wobbles just like a spinning top.
If in addition to the constant magnetic field, there is another magnetic field that varies at the same frequency as the nucleus wobbles, the nucleus will flip back and forth so that the nucleus effectively alternates the direction in which it spins. As the nucleus flips its spin direction, it either absorbs or emits low energy radio waves. Studying these radio waves allows physicists to deduce various properties of the atomic nuclei undergoing NMR.
Safety of NMR and MRI
Nuclear magnetic resonance uses the word nuclear because it involves the nucleus of the atom. It does not however in any way involve any dangerous radiation as people expect from nuclear weapons or other nuclear reactions. The only radiation patients are exposed to by nuclear magnetic resonance imaging is very low energy radio waves. Nuclear magnetic resonance imaging is therefore very safe. The word nuclear was dropped however to allay patient fears. To the average person magnetic resonance imaging sounds less dangerous than nuclear magnetic resonance, and MRI is very safe.
Magnetic Resonance Imaging
Magnetic resonance imaging is a very useful application of NMR. Medical MRI machines are designed to image the nuclei of the hydrogen atoms in the human body. Human bodies contain a high percentage of water, so there are a large number of hydrogen atoms in all human tissue. X-rays image bones well, but image other tissues very poorly. Magnetic resonance imaging therefore provides medical personnel with much better images of the soft tissue in the patient's body than X-rays can provide.
This article was found from the cite (http://physics.suite101.com/article.cfm/how_magnetic_resonance_imaging_mri_works)
Friday, November 27, 2009
Kinetic Energy
Kinetic energy is very simple it is the energy of motion. Objects that contain no motion has kinetic energy. "The faster the body moves the greater the kinetic energy produced. Also the greater the mass and speed of an object the greater the kinetic energy will be" This was found from the website <http://library.thinkquest.org/2745/data/ke.htm>
There are different types of kinetic energy. First there is vibrational which is the energy due to vibrational motion. Secondly there is rotational which is the energy due to rotational motion. Lastly there is translational, the energy due to the motion from one location to another.
Potential Energy
"Potential energy is the same as stored energy. The "stored" energy is held within the gravitational field. When you lift a heavy object you exert energy which later will become kinetic energy when the object is dropped. A lift motor from a roller coaster exerts potential energy when lifting the train to the top of the hill. The higher the train is lifted by the motor the more potential energy is produced; thus, forming a greater amount if kinetic energy when the train is dropped. At the top of the hills the train has a huge amount of potential energy, but it has very little kinetic energy." <http://library.thinkquest.org/2745/data/ke.htm>
Links Related To Kinetic Energy:
http://en.wikipedia.org/wiki/Kinetic_energy
http://www.physicsclassroom.com/Class/energy/U5l1c.cfm
There are different types of kinetic energy. First there is vibrational which is the energy due to vibrational motion. Secondly there is rotational which is the energy due to rotational motion. Lastly there is translational, the energy due to the motion from one location to another.
Potential Energy
"Potential energy is the same as stored energy. The "stored" energy is held within the gravitational field. When you lift a heavy object you exert energy which later will become kinetic energy when the object is dropped. A lift motor from a roller coaster exerts potential energy when lifting the train to the top of the hill. The higher the train is lifted by the motor the more potential energy is produced; thus, forming a greater amount if kinetic energy when the train is dropped. At the top of the hills the train has a huge amount of potential energy, but it has very little kinetic energy." <http://library.thinkquest.org/2745/data/ke.htm>
Links Related To Kinetic Energy:
http://en.wikipedia.org/wiki/Kinetic_energy
http://www.physicsclassroom.com/Class/energy/U5l1c.cfm
Radiography
Radiography
Radiography is the creation of images by exposing a photographic film or other image receptor to X-rays.
Since X-rays penetrate solid objects, but are weakened by them depending on the object's composition, the resulting picture reveals the internal structure of the object.
The most common use of radiography is in the medical field (where it is known as medical imaging), but veterinarians and engineers also use it..
<http://www.sciencedaily.com/articles/r/radiography.htm>
"Radiography is the use of X rays to view objects. It has been a big advancement in medical viewing. As said above radiography is used in the medical field but it is also used in the industrial field. Radiography was founded the same time X rays were discovered. X rays as we know are electromagnetic waves that do not require a medium to go through. This was learnt during our unit in physics on waves. From researching various cites i have found that radiography started in 1895. Radiography is very simple, all it is is the imaging of objects."
Radiography is the creation of images by exposing a photographic film or other image receptor to X-rays.
Since X-rays penetrate solid objects, but are weakened by them depending on the object's composition, the resulting picture reveals the internal structure of the object.
The most common use of radiography is in the medical field (where it is known as medical imaging), but veterinarians and engineers also use it..
<http://www.sciencedaily.com/articles/r/radiography.htm>
"Radiography is the use of X rays to view objects. It has been a big advancement in medical viewing. As said above radiography is used in the medical field but it is also used in the industrial field. Radiography was founded the same time X rays were discovered. X rays as we know are electromagnetic waves that do not require a medium to go through. This was learnt during our unit in physics on waves. From researching various cites i have found that radiography started in 1895. Radiography is very simple, all it is is the imaging of objects."
Speed of Sound
Speed of sound
The speed of sound is a term used to describe the speed of sound waves passing through an elastic medium.
The speed varies with the medium employed (for example, sound waves move faster through water than through air), as well as with the properties of the medium, especially temperature.
The term is commonly used to refer specifically to the speed of sound in air.
At sea level, at a temperature of 21 degrees Celsius (70 degrees Fahrenheit) and under normal atmospheric conditions, the speed of sound is 344 m/s (1238 km/h or 770 mph).
The speed varies depending on atmospheric conditions; the most important factor is the temperature.
Humidity has little effect on the speed of sound, nor does air pressure by itself. Air pressure has no effect at all in an ideal gas approximation.
This is because pressure and density both contribute to sound velocity equally, and in an ideal gas the two effects cancel out, leaving only the effect of temperature.Sound usually travels more slowly with greater altitude, due to reduced temperature..
The information provided was found from the website (http://www.sciencedaily.com/articles/s/speed_of_sound.htm)
"The speed of sound is something we learned during our unit on waves. The speed of sound is the disturbance through a medium. The speed of sound is different through different types of objects or substances. For example the speed of sound of air depends among the properties in air. It differs that from the speed of sound through various types of materials such as solids. The speed of sound in solids is greater then that of liquids. The speed of sounds in liquids is greater then that of gases. The speed of sound is one aspect we learned about when we took up our unit on waves. These were the different properties and aspects assosaited with the speed of sound."
The speed of sound is a term used to describe the speed of sound waves passing through an elastic medium.
The speed varies with the medium employed (for example, sound waves move faster through water than through air), as well as with the properties of the medium, especially temperature.
The term is commonly used to refer specifically to the speed of sound in air.
At sea level, at a temperature of 21 degrees Celsius (70 degrees Fahrenheit) and under normal atmospheric conditions, the speed of sound is 344 m/s (1238 km/h or 770 mph).
The speed varies depending on atmospheric conditions; the most important factor is the temperature.
Humidity has little effect on the speed of sound, nor does air pressure by itself. Air pressure has no effect at all in an ideal gas approximation.
This is because pressure and density both contribute to sound velocity equally, and in an ideal gas the two effects cancel out, leaving only the effect of temperature.Sound usually travels more slowly with greater altitude, due to reduced temperature..
The information provided was found from the website (http://www.sciencedaily.com/articles/s/speed_of_sound.htm)
"The speed of sound is something we learned during our unit on waves. The speed of sound is the disturbance through a medium. The speed of sound is different through different types of objects or substances. For example the speed of sound of air depends among the properties in air. It differs that from the speed of sound through various types of materials such as solids. The speed of sound in solids is greater then that of liquids. The speed of sounds in liquids is greater then that of gases. The speed of sound is one aspect we learned about when we took up our unit on waves. These were the different properties and aspects assosaited with the speed of sound."
Microwaves!!
Microwaves are electromagnetic waves with wavelengths longer than those of terahertz (THz) wavelengths, but relatively short for radio waves.
Microwaves have wavelengths approximately in the range of 30 cm (frequency = 1 GHz) to 1 mm (300 GHz).
However, the boundaries between far infrared light, terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study.
A microwave oven works by passing microwave radiation, usually at a frequency of 2450 MHz (a wavelength of 12.24 cm), through the food.
Water, fat, and sugar molecules in the food absorb energy from the microwave beam 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 induced by the microwave beam.
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)..
The information provided was found from the websited (http://www.sciencedaily.com/articles/matter_energy/physics/)
Microwaves have wavelengths approximately in the range of 30 cm (frequency = 1 GHz) to 1 mm (300 GHz).
However, the boundaries between far infrared light, terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study.
A microwave oven works by passing microwave radiation, usually at a frequency of 2450 MHz (a wavelength of 12.24 cm), through the food.
Water, fat, and sugar molecules in the food absorb energy from the microwave beam 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 induced by the microwave beam.
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)..
The information provided was found from the websited (http://www.sciencedaily.com/articles/matter_energy/physics/)
"As stated in the above article I've learned that microwaves are electromagnetic waves. Electromagnetic waves are waves that do not require a medium to go through. Microwaves are very good at transmitting information from one place to another. This is one used of microwaves. Another used microwaves have are that shorter microwaves are used in remote sensing. An example of this is weather forecasting. The most commom used of microwaves are those of microwave ovens or the kitchen appliance microwaves. The microwave radiation heats the water molecules within food. This results in the heating of your food but not completely baking your food. One interesting fact about microwaves were that they were first discovered in the 1940's."
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