The SEM produces a largely magnified image by using electrons instead of light to form an image. A beam of electrons is produced at the top of the microscope by an electron gun. It consists of an electron gun to produce high energy electron beam. A magnetic condensing lens is used to condense the electron beam and a scanning coil is arranged in-between magnetic condensing lens and the sample. The electron detector (Scintillator) is used to collect the secondary electrons and can be converted…
Photoacoustic spectroscopy (PAS) is a tool to study thermal emission resulting from non-radiative relaxation followed by absorption of radiation. PAS was studied primarily by Alexander Graham Bell, John Tyndall, Wilhelm Rontgen and Lord Rayleigh in 1884. For the history of PAS, was not until 1975 that photoacoustic spectroscopy started to be used as a wide range of different applications. This technique provides the following main advantages over the known types of spectroscopy. The advantages…
T Introduction Jean Piaget a well-known and first psychologist to make a systemic study of cognitive development. He was a very talented scholar and his first scientific paper, on the Albino Sparrow published at the age of ten. After he received his doctoral degree at the age of twenty-two, Piaget formally began his career that would have a profound impact on psychology and education. Today, Piaget is best known for his research on children’s cognitive development. He studied the intellectual…
observers. If you try to launch yourself off the Earth with a high speed and pulled a U-turn, you will return to the Earth in future. People on Earth would experience faster time than you that traveled with your rocket. The same with the speed, gravity also interferes with the flow of time (the other type of time dilation). A massive gravitational force from something just like the black hole which is for instance is so powerful that can bend any fabric of space-time around…
by describing light as a wave. Some other properties such as emission and absorption are better explained by treating light as a particle. The correct or exact nature of electromagnetic radiation is not clearly known, as it has the development of quantum mechanism in the first quarter of twentieth century. Wave properties of electromagnetic radiation Electromagnetic radiation consist of oscillating magnetic and electric…
Dostoevsky’s extended criticism of the world in his novel “Notes from the underground”, explores a dark truth about the human condition. The inevitably of suffering and the absence of consciousness is Dostoevsky’s example of the human condition that he perceives to be tragic but rather truthful. The protagonist whom represents the worldview of the Dostoevsky, tends to escape the 19th-century capitalist society of Russia by living underground and doing nothing. In this sense the retrospect of a…
creation of transistors was made possible by the Pauli exclusion principle, which states that each electron has a unique set of quantum numbers, and only two electrons can occupy the same orbital. Knowledge of the exclusion principle allowed developers like Shockley, Van Vleck, and Bardeen to create the transistor with semiconductors, which also rely heavily on quantum mechanics (they only allow a certain number of electrons through until a change occurs in the junctions of its positive and…
Molecular Orbital Theory (MOT): The VBT has two most serious limitations that electrons in molecules are treated as though they are localised and behave almost as they did in isolated atoms. This means that the VBT retains the individuality of the atoms composing molecule. The problem can be resolved by introducing the resonance theory, but with the loss of the original valence bond model. Hund[ 173], Mulliken[ 174], Van Vleck[175], Helsenberg[176], Jones[ 177] and others suggested an alternate…
An atomic model is a proposed idea of what an arrangement of an atom thought to look like. Many physicists such as Dalton Billiard, J.J. Thomson, Ernest Rutherford, and Neil Bohr proposed these ideas and made models based on their own ideas. Out of these physicists, Ernest Rutherford’s planetary model is the most generally accepted atomic model. Ernest Rutherford is a New Zealand born son to a Scottish wheelwright and an English schoolteacher. He did well in school academically as a child and…
Erwin Schrödinger was a physicist pioneer who gave a series of lectures in 1944. They were published under the title What is Life? (Harold, 2001). Though philosophical in nature, many have wondered if life can be reduced to biology or even further down to chemistry. This sent many scientists looking for the answer and spawned the guiding question, could human life be artificially created at the cellular level? This would consist of arranging the correct amounts of various elements into the…