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Principles of Spectroscopy Interaction of radiation and matter If matter is exposed to electromagnetic radiation, e.g. infrared light, the radiation can be absorbed, transmitted, reflected, scattered or undergo photoluminescence. Photoluminescence is a term used to designate a number of effects, including fluorescence, phosphorescence, and Raman scattering.   Electromagnetic Spectrum Type of Radiation Frequency :Range (Hz):Wavelength Range:Type of Transition Gamma-rays 1020-1024 <10-12 m nuclear X-rays 1017-1020 1 nm-1 pm inner electron Ultraviolet 1015-1017 400 nm-1 nm outer electron Visible 4-7.5x1014 750 nm-400 nm outer electron Near-infrared 1x1014-4x1014 2.5 mm-750 nm outer electron molecular vibrations Infrared 1013-1014 25 mm-2.5 mm molecular vibrations Microwaves 3x1011-1013 1 mm-25 mm molecular rotations, electron spin flips* Radio waves <3x1011 >1 mm >1 mm TYPES OF OPTICAL INSTRUMENTS • Spectroscope: uses human eye as a detector • Spect...

Solid-state physics is the study of rigid matter , or solids , through methods such as quantum mechanics , crystallography , electromagnetism, and metallurgy . It is the largest branch of condensed matter physics . Solid-state physics studies how the large-scale properties of solid materials result from their atomic -scale properties. Thus, solid-state physics forms a theoretical basis of materials science . It also has direct applications, for example in the technology of transistors and semiconductors . Solid materials are formed from densely packed atoms, which interact intensely. These interactions produce the mechanical (e.g. hardness and elasticity ), thermal , electrical , magnetic and optical properties of solids. Depending on the material involved and the conditions in which it was formed, the atoms may be arranged in a regular, geometric pattern ( crystalline solids , which include metals and ordinary water ice ) or irregularly (an amorphous solid such as common ...

A nuclear reaction is considered to be the process in which two nuclear particles (two nuclei or a nucleus and a nucleon) interact to produce two or more nuclear particles or ˠ-rays (gamma rays). Thus, a nuclear reaction must cause a transformation of at least one nuclide to another. Sometimes if a nucleus interacts with another nucleus or particle without changing the nature of any nuclide, the process is referred to a nuclear scattering, rather than a nuclear reaction. Perhaps the most notable nuclear reactions are the nuclear fusion reactions of light elements that power the energy production of stars and the Sun. Natural nuclear reactions occur also in the interaction between cosmic rays and matter. Nuclear reactors are devices to initiate and control a chain nuclear reaction, but there are not only manmade devices. The world’s first nuclear reactor operated about two billion years ago. The natural nuclear reactor formed at Oklo in Gabon, Africa, when a uranium-ri...

Nuclear Stability is a concept that helps to identify the stability of an isotope. To identify the stability of an isotope it is needed to find the ratio of neutrons to protons. To determine the stability of an isotope you can use the ratio neutron/proton (N/Z). Also to help understand this concept there is a chart of the nuclides, known as a Segre chart. This chart shows a plot of the known nuclides as a function of their atomic and neutron numbers. It can be observed from the chart that there are more neutrons than protons in nuclides with Z greater than about 20 (Calcium). These extra neutrons are necessary for stability of the heavier nuclei. The excess neutrons act somewhat like nuclear glue. Atomic nuclei consist of protons and neutrons, which attract each other through the nuclear force , while protons repel each other via the electric force due to their positive charge. These two forces compete, leading to various stability of nuclei. There are only certain com...

adiation Most general definition is that radiation is energy that comes from a source and travels through some material or through space. Light, heat and sound are types of radiation. This is very general definition, the kind of radiation discussed in this article is called ionizing radiation . Most people connect the term radiation only with ionizing radiation, but it is not correct. Radiation is all around us. In, around, and above the world we live in. It is a natural energy force that surrounds us. It is a part of our natural world that has been here since the birth of our planet. We should distinguish between: Non-ionizing radiation . The kinetic energy of particles ( photons, electrons, etc. ) of non-ionizing radiation is too small to produce charged ions when passing through matter. The particles (photons) have only sufficient energy to change the rotational, vibrational or electronic valence configurations of target molecules and atoms. Sunlight, radio waves...

A knowledge of atomic and nuclear physics is essential to nuclear engineers , who deal with nuclear reactors . It should be noted that atomic and nuclear physics is very extensive branch of science. Nuclear reactor physics belongs to an applied physics. Reactor physics, particle physics or other branches of modern physics have common fundamentals. Atomic and nuclear physics describes fundamental particles (i.e. electrons, protons, neutrons ), their structure, properties and behavior. Atomic and nuclear physics are not the same. The term atomic physics is often associated with nuclear power, due to the synonymous use of atomic and nuclear in standard English. However, physicists distinguish between atomic and nuclear physics. The atomic physics deals with the atom as a system consisting of a nucleus and electrons . The nuclear physics deals with the nucleus as a system consisting of a nucleons (protons and neutrons) . Main difference is in the scale . While the term atomi...

The degree of hotness or coldness of a body or environment. A measure of the warmth or coldness of an object or substance with reference to some standard value. A measure of the average kinetic energy of the particles in a sample of matter, expressed in terms of units or degrees designated on a standard scale. A measure of the ability of a substance, or more generally of any physical system, to transfer heat energy to another physical system. Any of various standardized numerical measures of this ability, such as the Kelvin, Fahrenheit, and Celsius scale As mentioned , the first two bullet points have rather obvious meanings. The third bullet point was the topic of  the previous page in this lesson . The fifth bullet point was the definition that we started with as we discussed temperature and the operation of thermometers; it was the topic of  the second page in this lesson . That leaves us with the fourth bullet point - defining temperature in terms of the ability o...

Heat, energy and temperature pervade our lives. Just think about it. We give attention to hot and cold in deciding what we wear during the day, at night and when we go to bed. We think about the topic when deciding how many covers, if any at all, we will wrap in or sleep under at night in order to maintain  the right temperature . Many of us have heating and cooling systems in our homes, schools and work places that control the temperature during the day and night to keep us as comfortable as possible without spending too much money. We install fans or use portable fans in our homes to keep us comfortable. Most of us have cars equipped with heating and air conditioning systems; some may even have meters in their cars that register the indoor and outdoor temperatures. Many of us watch and listen to weather reports, especially the forecasted temperatures, with great interest so that we can make decisions about what to wear and what to do on the following day Our bodies are highly ...

Magnetic Fields  Force On A Current Carrying Wire In A Magnetic Field You will be familiar with the basic notion of a magnetic field , in which magnetic materials experience a magnetic force.  However it is worth revising some of the basic ideas that you will have come across in early secondary school. Revision Magnetic fields can be shown by field lines, which go from North to South. The field lines in a strong magnetic field are more closely packed than in a weak field. Unmagnetised materials are attracted to either pole. Like poles repel; unlike poles attract. In the Earth’s magnetic field, the North pole will align itself to point to the North, if the magnet is allowed to swing freely. The Earth has a magnetic field like a bar magnet.  Notice that the S-pole is under the North geographic pole.  Be careful not to be confused by ...

In ancient times Greece people found a rock that attracts iron, nickel and cobalt. They call them as “magnet “and magnetism comes from here. These rocks were used later by Chinese people to make compasses. Later scientists found that, magnets have always two poles different from electricity. Magnets have two ends or faces called “poles” where the magnetic effect is highest. In last unit we saw that there is again two polarities in electricity, “-“charges and “+” charges. Electricity can exist as monopole but magnetism exists always in dipoles North Pole (represented by N ) and South Pole (represented by S) . If you break the rock into pieces you get small magnets and each magnet also has two poles N and S. Same poles of the magnet like in the electricity repel each other and opposite poles attract each other. Strengths of these forces depend on the distance between the poles and intensity of the poles. Types of Magnets In nature Fe 3 O 4 is used as magnet. However, th...