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- 2. “Quantum physics can’t be visualised.”
- What Has Quantum Mechanics Ever Done For Us?
Unless my grumpy correspondent was posting from the exact server hosting the comment files which would be really creepy , odds are very good that comment took a path to me that also relies on quantum physics, specifically fiber optic telecommunications. The fibers themselves are pretty classical, but the light sources used to send messages down the fiber optic cables are lasers, which are quantum devices. This introduces the idea of stimulated emission, where an atom in a high-energy state encountering a photon of the right wavelength is induced to emit a second photon identical to the first.
Any time you use a laser, whether indirectly by making a phone call, directly by scanning a UPC label on your groceries, or frivolously to torment a cat, you're making practical use of quantum physics. One of the most common uses of Internet-connected smart phones is to find directions to unfamiliar places, another application that is critically dependent on quantum physics. Smartphone navigation is enabled by the Global Positioning System, a network of satellites each broadcasting the time.
The GPS receiver in your phone picks up the signal from multiple clocks, and uses the different arrival times from different satellites to determine your distance from each of those satellites. The computer inside the receiver then does a bit of math to figure out the single point on the surface of the Earth that is that distance from those satellites, and locates you to within a few meters.
This trilateration relies on the constant speed of light to convert time to distance. Light moves at about a foot per nanosecond, so the timing accuracy of the satellite signals needs to be really good, so each satellite in the GPS constellation contains an ensemble of atomic clocks. Any time you use your phone to get you from point A to point B, the trip is made possible by quantum physics.
Leila Wehbe, a Ph. Images showing combinations of data and graphics were collected. Those spins are an intrinsically quantum phenomenon actually, it comes in only when you include special relativity with quantum mechanics , causing the electrons, protons, and neutrons making up ordinary matter behave like tiny magnets. This spin is responsible for the fourth and final practical application of quantum physics that I'll talk about today, namely Magnetic Resonance Imaging MRI.
A clever arrangement of magnetic fields lets doctors measure the concentration of hydrogen appearing in different parts of the body, which in turn distinguishes between a lot of softer tissues that don't show up well in traditional x-rays.
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So any time you, a loved one, or your favorite professional athlete undergoes an MRI scan, you have quantum physics to thank for their diagnosis and hopefully successful recovery. So, while it may sometimes seem like quantum physics is arcane and remote from everyday experience a self-inflicted problem for physicists, to some degree, as we often over-emphasize the weirder aspects when talking about quantum mechanics , in fact it is absolutely essential to modern life.
Semiconductor electronics, lasers, atomic clocks, and magnetic resonance scanners all fundamentally depend on our understanding of the quantum nature of light and matter. Each chip on the silicon "wafer" Otellini showed off has 2.
The key physics of the laser is contained in a paper Einstein wrote on the statistics of photons though the term "photon" was coined later and their interaction with atoms. This process is responsible for two of the letters in the word "laser," originally an acronym for "Light Amplification by Stimulated Emission of Radiation.
The image changes as the position and orientation of the viewing system changes in exactly the same way as if the object were still present, thus making the image appear three-dimensional. Laser: Holograms are recorded using a flash of light that illuminates a scene and then imprints on a recording medium, much in the way a photograph is recorded. In addition, however, part of the light beam must be shone directly onto the recording medium — this second light beam is known as the reference beam ].
A hologram requires a laser as the sole light source.
Laser is required as a light source to produce an interference pattern on the recording plate. To prevent external light from interfering, holograms are usually taken in darkness, or in low level light of a different color from the laser light used in making the hologram. Holography requires a specific exposure time, which can be controlled using a shutter, or by electronically timing the laser. Recording a hologram : Holograms are recorded using a flash of light that illuminates a scene and then imprints on a recording medium, much in the way a photograph is recorded.
In addition, however, part of the light beam must be shone directly onto the recording medium — this second light beam is known as the reference beam. Apparatus: A hologram can be made by shining part of the light beam directly onto the recording medium, and the other part onto the object in such a way that some of the scattered light falls onto the recording medium.
A more flexible arrangement for recording a hologram requires the laser beam to be aimed through a series of elements that change it in different ways. The first element is a beam splitter that divides the beam into two identical beams, each aimed in different directions:. Reconstructing a hologram : An interference pattern can be considered an encoded version of a scene, requiring a particular key — the original light source — in order to view its contents.
This missing key is provided later by shining a laser, identical to the one used to record the hologram, onto the developed film. This produces a light field identical to the one originally produced by the scene and scattered onto the hologram. Several different materials can be used as the recording medium. One of the most common is a film very similar to photographic film silver halide photographic emulsion , but with a much higher concentration of light-reactive grains, making it capable of the much higher resolution that holograms require.
A layer of this recording medium e. Process: When the two laser beams reach the recording medium, their light waves intersect and interfere with each other. It is this interference pattern that is imprinted on the recording medium. The interference pattern can be considered an encoded version of the scene, requiring a particular key — the original light source — in order to view its contents. A periodic table is a tabular display of elements organized by their atomic numbers, electron configurations, and chemical properties.
The periodic table is a tabular display of the chemical elements.http://www.cantinesanpancrazio.it/components/maqenuwy/282-trovare-password.php
A Physics Book List
The elements are organized based on their atomic numbers, electron configurations, and recurring chemical properties. In the periodic table, elements are presented in order of increasing atomic number the number of protons. The rows of the table are called periods; the columns of the s- columns and He , d- columns , and p-blocks columns , except He are called groups. Some groups have specific names, such as the halogens or the noble gases. Since, by definition, a periodic table incorporates recurring trends, any such table can be used to derive relationships between the properties of the elements and predict the properties of new, yet-to-be-discovered, or synthesized elements.
As a result, the periodic table provides a useful framework for analyzing chemical behavior, and such tables are widely used in chemistry and other sciences. Blocks in the Periodic Table : A diagram of the periodic table, highlighting the different blocks. Although precursors exist, Dmitri Mendeleev is generally credited with the publication, in , of the first widely recognized periodic table. Agroup, or family, is a vertical column in the periodic table. Groups usually have more significant periodic trends than do periods and blocks, which are explained below.
Modern quantum mechanical theories of atomic structure explain group trends by proposing that elements in the same group generally have the same electron configurations in their valence or outermost, partially filled shell. Consequently, elements in the same group tend to have shared chemistry and exhibit a clear trend in properties with increasing atomic number. However, in some parts of the periodic table, such as the d-block and the f-block, horizontal similarities can be as important as, or more pronounced than, vertical similarities.
A period is a horizontal row in the periodic table. Although groups generally have more significant periodic trends, there are regions where horizontal trends are more significant than vertical group trends, such as in the f-block, where the lanthanides and actinides form two substantial horizontal series of elements. Elements in the same period show trends in atomic radius, ionization energy, and electron affinity.
Atomic radius usually decreases from left to right across a period. This occurs because each successive element has an added proton and electron, which causes the electron to be drawn closer to the nucleus, decreasing the radius. The periodic table : Here is the complete periodic table with atomic numbers, groups, and periods. Each entry on the periodic table represents one element, and compounds are made up of several of these elements.
X-rays are a form of electromagnetic radiation and have wavelengths in the range of 0. X-radiation composed of x-rays is a form of electromagnetic radiation. X-rays have wavelengths in the range of 0. X-Ray Spectrum and Applications : X-rays are part of the electromagnetic spectrum, with wavelengths shorter than those of visible light. Different applications use different parts of the X-ray spectrum.
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X-rays can be generated by an x-ray tube, a vacuum tube that uses high voltage to accelerate the electrons released by a hot cathode to a high velocity. The high-velocity electrons collide with a metal target, the anode, creating the x-rays.
The maximum energy of the produced x-ray photon is limited by the energy of the incident electron, which is equal to the voltage on the tube times the electron charge, so an kV tube cannot create x-rays with an energy greater than 80 keV. When the electrons hit the target, x-rays are created through two different atomic processes:. Both of these x-ray production processes are inefficient, with a production efficiency of only about one percent.
Therefore, to produce a usable flux of x-rays, most of the electric power consumed by the tube is released as heat waste. The x-ray tube must be designed to dissipate this excess heat. A specialized source of x-rays that is becoming widely used in research is synchrotron radiation, which is generated by particle accelerators.
2. “Quantum physics can’t be visualised.”
Its unique features are x-ray outputs many orders of magnitude greater than those of x-ray tubes, wide x-ray spectra, excellent collimation, and linear polarization. Atom is a basic unit of matter that consists of a nucleus surrounded by negatively charged electron cloud, commonly called atomic orbitals.
The atom is a basic unit of matter that consists of a nucleus surrounded by negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons. The electrons of an atom are bound to the nucleus by the electromagnetic Coulomb force. Atoms are minuscule objects with diameters of a few tenths of a nanometer and tiny masses proportional to the volume implied by these dimensions.
What Has Quantum Mechanics Ever Done For Us?
Atoms in solid states or, to be precise, their electron clouds can be observed individually using special instruments such as the scanning tunneling microscope. In , physicist Niels Bohr suggested that the electrons were confined into clearly defined, quantized orbits, and could jump between these, but could not freely spiral inward or outward in intermediate states. An electron must absorb or emit specific amounts of energy to transition between these fixed orbits. A consequence of using waveforms to describe particles is that it is mathematically impossible to obtain precise values for both the position and momentum of a particle at the same time; this became known as the uncertainty principle, formulated by Werner Heisenberg in Thereafter, the planetary model of the atom was discarded in favor of one that described atomic orbital zones around the nucleus where a given electron is most likely to be observed.
Illustration of the Helium Atom : This is an illustration of the helium atom, depicting the nucleus pink and the electron cloud distribution black. The nucleus upper right in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case. The black bar is one angstrom m, or pm. Quantum electrodynamics QED , a relativistic quantum field theory describing the interaction of electrically charged particles, has successfully predicted minuscule corrections in energy levels.