Guang-tsai Lei has written:
'Investigation of radar backscattering from second-year sea ice' -- subject(s): Radar, Backscattering
1 answer
Backscattering refers to the reflection of a portion of the energy from a wave or particle back in the direction from which it came. It is commonly observed in radar systems and can provide valuable information about the target being surveyed. Backscattering is utilized in various applications, including remote sensing and medical imaging.
3 answers
M. B Lewis has written:
'Analysis of a nuclear backscattering and reaction data by the method of convolution integrals' -- subject(s): Chemical reactions, Convolutions (Mathematics), Backscattering
1 answer
Rainbows are caused by backscatter. If the sun is out, and it is raining, look in the direction opposite from the sun, and you may see a rainbow.
1 answer
W. C. Neely has written:
'X-ray photoelectron spectroscopy (XPS), Rutherford back scattering (RBS) studies ..' -- subject(s): Aluminun alloys, Auger spectroscopy, Backscattering, Electron transitions, Photoelectron spectroscopy, X ray spectroscopy
1 answer
Willard J Pierson has written:
'A Monte Carlo comparison of the recovery of winds near upwind and downwind from the SASS-1 model function by means of the sum of squares algorithm and a maximum likelihood estimator' -- subject(s): Backscattering, Scattering (Physics)
1 answer
The fact that the vast majority of the alpha particles got straight through led Rutherford to propose that the atom was composed primarily of empty space.
The fact that backscattering occurred in 1 in 8000 alpha particles indicated that there was a small massive positively charged nucleus in the centre of the atom.
1 answer
D. W. Bogdanoff has written:
'CFD modelling of bore erosion in two-stage light gas guns' -- subject(s): Computational fluid dynamics, Gas pressure, Powder (Particles), Solar radiation, Igniters, Backscattering
4 answers
Beta radiation is used to measure thickness because it has low penetration power, allowing it to measure thin materials without passing through them. This makes it ideal for applications where precise measurement of thin materials is required, such as in the manufacturing industry. Additionally, beta radiation can easily be detected and measured, providing fast and accurate results.
4 answers
Rutherford showed that the atom consisted of a very dense and very small core (the nucleus), and that the rest was mostly empty space (the electron cloud). By using a backscattering experiment, he watched how alpha particles passed through a very thin gold foil. He found that most of the alpha passed right through the foil with no change in their original direction. However some did change direction, and the ones that did, changed directly significantly. In other words, most of the particles passed through the atoms like nothing was there, but a few hit something as if they hit a brick wall!
Bohr's model of the atom didn't address the question of structure in this way. The Bohr model was used to explain the energy levels of atoms and how atoms absorb and emit light. See the Related Questions to the left for a more complete description of the Bohr model of the atom.
The Bohr model said electrons travel in fixed, circular orbits about the nucleus. We know now that we cannot predict the exact location of an electron in any point in time, and that these electrons exist in "orbitals", and don't travel in circular paths around the nucleus. It is explained by the Heisenberg Uncertainty Principle. The new atomic theory says that electrons are both waves and particles. It is said that just "looking" at an electron (figuratively) would change its position in the atom.
1 answer
We can't say with any great certainty what the weather patterns will be like, but current studies using a variety of methods, suggest that if the amount of Carbon Dioxide (CO2) in the atmosphere doubles (that is, from 280 ppm to 560 ppm) the temperature rise could be anywhere between 2 and 5°C. Best estimates are pointing to a rise of 3°C with a likely maximum of 4.5°C. The amount of this rise is what is known as 'climate sensitivity'. (Scientists also say that anything over two degrees of rise will be catastrophic!)
Temperature drives climate. Changes in temperature cause changes in pressure, which means changes in winds, which means changes to rainfall patterns. And higher temperatures mean more changes.
Current predictions for climate change include more severe and more frequent weather events like cyclones, floods, tornadoes and droughts.
Another View:
Some climate experts believe that there is a saturation point for carbon dioxide levels and that an increase above this point will cause little, if any, increase in temperatures. Should CO2 levels double, the peer reviewed paper by Hermann Harde (2011) points out that his research indicates that the IPCC is seven times higher than his data suggests.
He claims an increase of: 0.41°C for the tropical zone, 0.40°C for the moderate zones and CS = 0.92°C for the polar zones. The weighted average over all regions as the global climate sensitivity is found to be 0.45°C with an estimated uncertainty of 30%, which mostly results from the lack of more precise data for the convection between the ground and atmosphere as well as the atmospheric backscattering.
1 answer
If Rutherford had bombarded aluminum foil with alpha particles instead of gold foil, he would have observed that most of the alpha particles would pass through the foil with minimal deflection since aluminum is a lighter element compared to gold. Some of the alpha particles may undergo slight scattering or deflection due to interactions with the atomic nuclei in the aluminum foil, but there would be no significant backscattering as seen in the gold foil experiment.
6 answers
In Rutherford's experiment, alpha particles were aimed at a thin sheet of gold foil. Most of the alpha particles passed straight through, but some were deflected at large angles. This led to the conclusion that atoms have a small, positively charged nucleus at their center.
9 answers
According to Thomson's atomic theory, the mass of an atom was special evenly throughout its volume. Errest Rutherford's experiment proved this wrong.
6 answers
A microscope is a magnifying imaging device used to examine very tiny things. An optical microscope can be used on such things as live blood cells, or live tissue cultures from a petri dish. The samples are either extremely thin (or made so using a slice cutting instrument) so that a light source can be projected up through the sample into the optical magnifying lens stages of the instrument, and then finally into either a camera, or a person's eye(s). Magnification levels of a conventional laboratory optical microscope typically range from 10 times power, up to about 2500 times power. Other rarely used, special, extremely expensive optical microscopes have used scanning lasers, or used wavelengths of light outside of human perception with backscattering / heterodyning, aspherical lenses, multiple staged prisms, quartz optics, etc., to achieve higher magnification, and some of these have variable field depth of focus. A scanning electron microscope can have extremely high magnification, but must typically pre-treat the sample to be examined by using a process that kills any live samples, sometimes coating them with a deposit of metal such as gold, etc, and then the sample is subjected to a near perfect vacuum also insuring that the sample is dead. Newer two-photon scanning microscopes have recently been invented, and may also be used on live samples of tiny living things without first killing them. A computer aided tomographic scan is a 3-D x-ray imaging technology that extends the usefulness of 2-D gray scale x-rays. X-ray technology typically neither magnifies nor reduces the size of the subject image--so that the images are "life-sized." Tomography consists of taking many angles of 1-dimensional x-ray beams into carefully aligned sensors that are used in mathematical combinations to compute the various tissue densities encountered by the various x-ray beams travelling through the tissues to all of the various sensors at all of their various angles with respect to the sample and the x-ray source(s). This makes up one of many 2-D x-ray slices that are then combined as an array to form a 3-D image also through carefully calculated mathematical combinations. X-rays are a form of very high frequency electromagnetic radiation called ionizing radiation that is typically harmful to living cells. The x-ray source units typically consist of a high voltage power supply, an Edison-effect electron source such as a tungsten filament, and a target tungsten x-ray emitter. The high voltage accelerates the electrons from the source to a very high energy speed onto the tungsten target x-ray emitter. Every chemical element has an emission and absorption frequency spectrum of energy. The energy from the high speed / energy electrons is first absorbed (large amounts of medium frequency energy) into the tungsten target x-ray emitter, and when the atoms of the tungsten then can contain no more energy, they then release this excess energy (emission) in the form of electromagnetic energy in the frequency spectrum of two key bands of x-ray radiation (which is the emission spectrum of the metal chemical element tungsten). This radiation can penetrate through all sorts of material. By moderating the output levels of x-ray energy to only those necessary to penetrate a given sample type, either a sensor or a piece of photographic film can record the projected energy from the x-ray source that makes its way through the sample under imaging analysis. High density tissues like bones will block the x-rays more than softer tissues like muscles or liver or kidneys. Sometimes a liquid metal such as barium is used to fill the upper or lower gastrointestinal (GI) tract to better help the imaging results since barium will also block x-rays more than the other soft surrounding tissues. The barium filled cavities of the GI tract will nicely outline the borders of those cavities so that any irregularities can be quickly seen in the resulting images. X-rays can be used to detect defects in pipe steel used for cooling nuclear reactors, or car parts or welded pieces, or in medicine to look through the various tissues of a bird or mammal like a pet dog or a human being. Different forms of imaging can be used to identify both the symptoms and causes of disease. Other forms of medical imaging include thermal image scanners, positron emission tomographic scanners, and scanners that provide a combination of these tomographic imaging methods to better identify and diagnose unusual tissues (cancer) or blood flow activity (damaged tissues). In some cases the cause of disease can be microscopic, but result in large-scale damage or cancerous tissues. However, prolonged exposure to radiation levels of x-rays can burn tissues, cause cancer, or be used as a means of burning tissues on purpose as in some forms of cancer treatment. Cancer tumors, however, engulf or intermingle with nearby healthy tissues that are more sensitive to the harmful effects of x-rays than the cancerous ones. In some cases the mass of a tumor under radiation therapy diminishes in proportion to the amount of nearby healthy tissue that is burned / damaged by radiation treatment rather than destroying the actual cancerous part of the tissue, thereby deceiving both the patient and the doctors into thinking that the tumor shrinkage equates to the cancer being eliminated when only the healthy tissue has been instead. It is highly probable that the true nature of certain diseases is still not properly understood, but the imaging technology to monitor disease progression can be applied to determine if a treatment is effective if applied after a week or so time of treatment recovery.
1 answer