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Nanoparticles and Its Properties

Introduction: The prefix 'nano' means a billionth ($10^{-9}$). The field of nanotechnology is the study of various structures of matter having dimensions of the order of a billionth of a meter. These particles are called nanoparticles. Nanotechnology is based on the fact that particles that are smaller than about $100 nm$ give rise to new properties of nanostructures built from them. Particles that are smaller than the characteristic length for a particular phenomenon show different physical and chemical properties than particles of larger sizes. For example, mechanical properties, optical properties, conductivity, melting point, and reactivity have all been observed to change when particles become smaller than the characteristic length. Gold and silver nanoparticles were used in window glass panes to obtain a variety of beautiful colors. Nanotechnology has a wide range of applications like producing lighter but stronger materials, constructing faster switches for comput

Difference Between Prism Spectra and Grating Spectra

Prism Spectra 1.) Prism spectra are obtained by the phenomena of dispersion of light. 2.) Prism spectra have only one order. 3.) A prism spectrum is of bright intensity. 4.) In prism spectra, spectral colors overlap each other. 5.) Red color is dispersed least whereas violet color disperses the maximum. 6.) Prism spectrum depends upon the material of prism. 7.) The prism spectral lines are curved. . Grating Spectra 1.) Grating spectra are obtained by the phenomena of diffraction of light. 2.) Grating spectra has more than one order. 3.) Grating spectra is of less intensity. 4.) In grating spectra, there is no overlapping of color. 5.) Red color diffracts the maximum whereas violet color diffracts the least. 6.) Grating spectra are independent of the material of grating. 7.) The grating spectral lines are almost straight.

Difference between interference and diffraction

Interference 1.) It is due to the superposition of two or more than two wavefronts coming from coherent sources. 2.) The intensity of all bright fringes are same 3.) Interference fringes either of the same size or decrease after moving away from the center. 4.) Dark fringes are usually perfectly dark. 5.) A minimum coherent source is needed. Diffraction: 1.) It occurs due to secondary wavelets, originating from infinite different points of the same wavefronts. 2.) Central maxima of bright fringe is followed by either side maxima of decreasing intensity. 3.) Interference fringes are never of the same shape and size. 4.) Dark fringes are not perfectly dark. 5.) It is possible by either one or more than one source which need not be coherent.

Superconductors and its properties

Superconductivity The property of a substance in which the electrical resistance of the substance is zero at very low temperatures. This property of substance is called superconductivity. For certain substances, like mercury, the resistivity suddenly drops to zero at very low temperatures typically near the boiling point of liquid helium. Some metals, doped semiconductors, alloys and ceramics (i.e. these are insulators at room temperature and superconduct at higher temperatures than the metals) show superconductivity. Temperature Dependence of Resistivity In superconducting substances, the resistivity suddenly drops to zero at a particular temperature known as critical temperature ($T_{c}$) or transition temperature and remains zero below that as shown in Figure below. The critical temperature for mercury is $4.2 K$. Below this critical temperature, mercury is superconducting whereas above this temperature it behaves like a normal conductor. Different superconducting

Kinetic Theory of Ideal Gases

German scientists R.Classius and J.C. Maxwell had propounded the kinetic theory of gases. According to this model, every gas is made up of very fine particles called molecules. All the molecules of a gas are similar in all properties. We know that $ 1 cm^{3}$ of water at $100^{\circ}C$ temperature and $1$ atmosphere pressure produces $1671 cm$ of water vapour. From this, it is known that the volume actually occupied by the molecules in $1671 cm^{3}$ of water vapour is only $1 cm^{3}$ and the remaining $1670 cm^{3}$ of volume is empty. In other words, we can say that in the gaseous state of matter, there is a lot of free space between the molecules. This fact is true for all gases. The molecules of gases are always moving randomly in all possible directions. During motion, these molecules collide with each other and with the walls of the vessel in which the gas is kept. After each collision, both the direction and speed of motion of these molecules keep changing. All collisions betw

Newton's Corpuscular Model

Newton's Corpuscular Theory In the year 1675, Newton proposed the corpuscular theory of light to explain the existing phenomenon of light. There are the following assumptions of this theory: 1. The light consists of very small, lightweight, and invisible particles. These particles are known as corpuscles. 2. These corpuscles move with the velocity of light in a homogeneous medium in all possible directions in a straight line and they carry kinetic energy with them. 3. When these corpuscles fall on the retina of the eye, they produce the sensation of vision. 4. The size of corpuscles of different colors is different (ie, the color of light depends on the size of the corpuscle). (A) Success of Carpuscles Theory Based on this theory, the following facts related to light were explained successfully: 1. The light has energy: Since corpuscles have kinetic energy. Therefore, the energy of the light beam is due to the kinetic energy of the corpuscles. 2. Motion

Nuclear force and its properties

Nuclear Force A forces that act between the nucleons (i.e proton and neutron) inside the nucleus. This force is called the nuclear force. These forces are responsible to keep the nucleons bound inside the nucleus. Properties of Nuclear Force There are the following properties of nuclear force is given below. (i) These are strong nuclear forces otherwise protons cannot exist in the nucleus. (ii) The intensity of these forces is very large. The intensity of nuclear force is maximum among, so far known forces. (iii) It is not electrical in nature. If we assume them electrical forces, then the protons cannot reside in nucleus. (iv) These forces do not depend on charge. The force acting between the nucleons (such as proton-proton, neutron-neutron and proton-neutron) is of same nature. (v) These are not gravitational forces because the mass of the particles inside the nucleus is very small, while the magnitude of nuclear force is very large. (vi) These

Limitations of Bohr's Model

Although Bohr's model of hydrogen atom and hyarogen like atom was successful in explaining the stability and spectrum even then it has few limitations. which are as follows: (1) This model could not explain the spectrum of atom having more than one electron. (2) This model could not explain the relative intensity of spectral lines. (i. e., few transitions are more acceptable than others why?) (3) When a spectral line is observed by spectroscope of high resolution power, more than one lines are observed. This is known as fine structure of spectral line. Bohr model could not explain this. (4) Splitting of spectral lines in external magnetic field (Zeeman's effect) and in external electric field (Stark's effect) could not be explained by this model. (5) This model could not explain the distribution of electrons in different orbit. Few limitations of Bohr's model are removed in Somer-field's model of atom. (In this model, the orbit of electron was

Comparison of Isothermal and Adiabatic Processes for an Ideal Gas

Isothermal Process: 1.) In this process temperature remains constant i.e.$(\Delta T= 0)$. 2.) In this process internal energy remains constant i.e. $(\Delta U= 0)$. 3.) This process takes place very slowly. 4.) In this process the system is surrounded by a perfectly conducting material, whose conductivity is infinite. 5.) This process obeys Boyle's law i.e. $(PV= constant)$. 6.) In this process the slope of isothermal curve $=-\frac{P}{V}$ 7.) In this process specific heat of gas should be infinite. Adiabatic Process: 1.) In this process exchange of heat does not take place i.e. $(\Delta Q= 0)$ but temperature changes. 2.) In this process internal energy changes. 3.) This process takes place very rapidly. 4.) In this process the system is surrounded by a perfectly insulating material, whose conductivity is zero. 5.) This process obeys Poisson's law i.e. $(PV^{\gamma} = constant)$. 6.) In this process the slope of adiabatic curve $=-

Concept of Perfect Gas

Concept of Perfect (ideal) Gas: An imaginary gas whose properties are similar to the properties of a real gas (a gas whose molecules occupy space and interact with each other) at infinitely low pressure. This imaginary gas is called 'perfect gas' or ideal gas'. According to the definition, the following properties are imagined in a perfect gas : (1) It strictly obeys Boyle's law, Charles' law, and the law of pressure under all conditions of temperature and pressure. (2) Its pressure coefficient and volume coefficient are exactly equal to each other. (2) Its molecules are infinitesimally small. (3) There is no force of attraction between its molecules. Obviously, a perfect gas cannot be converted into a liquid or solid state, because a force of attraction is necessary between the molecules in the liquid or the solid state. In practice, the gases that are difficult to liquefy, such as oxygen, nitrogen, hydrogen, and helium can be considered as p

Failure of Wave Theory in Explaining Photoelectric Emission Effect

Description of failure of wave theory in explaining photoelectric effect: Although reflection, refraction, interference, diffraction and polarisation etc. are explained on the basis of wave theory but the laws of photoelectric effect cannot be explained on the basis of the wave theory of light. There are three main reasons for failure: 1.) According to wave theory, as the intensity of incident light increases, incident energy also increases. Therefore, greater is the intensity, greater will be the energy absorbed by the electrons of metal and therefore greater should be the kinetic energy of photoelectrons. From experimental observations, it is clear that the maximum kinetic energy of photoelectrons does not depend on the intensity of incident light. 2.) According to wave theory, photoelectric emission should occur for all the frequencies provided that it has enough energy to emit the electrons from the metal. Although from experimental observation it is clear that if the fre