Duduli

It is the energy that remains in a system even when it's at its lowest possible energy state, which is typically at absolute zero temperature. Zero point energy refers to the lowest possible energy that a quantum mechanical physical system may have. At low temperatures, most of the oscillators are in the state of zero point energy (hv/2). They execute zero point oscillations and not thermal oscillations.

The characteristics of the elastic vibrational motion of crystal lattice are called as lattice vibrations. In order to understand the vibrations in 1-D(linear) lattice following assumptions are made (i) All the atoms are arranged on a straight line with constant interatomic spacing 'a'. (ii) The atoms are identical having same mass 'm'. (iii) Interaction between the atoms extends only upto the nearest neighbours i.e lattice is characterized by short range forces.(Hooke's law is obeyed) (iv) Each atom is connected with its neighbours by a massless spring with force constant.

A device for tabulating both the slopes & the interplanar spacings of the Planes of a crystal lattice is provided by the concept of reciprocal lattice. General procedure for locating reciprocal lattice points:- → A lattice point is taken as common origin. → From the common origin, draw a normal to each plane. → Place a point on the normal to each plane (h k l) at a distance from the origin equal to 1/d(h k l). → Such points form a periodic array called reciprocal lattice.

Type i superconductor is one in which the transition from superconductivity state to normal state in presence of magnetic field occurs sharply at the critical value Hc. ★ They are perfectly diamagnetic. ★ They follow meissner effect strictly. ★ The critical value Hc for type i   superconductors is found to be very   low, i.e for small value of Hc it behaves   normal conductor therefore it is known   as soft superconductor.

A domain is a region in which all the atoms are arranged in such a way that their magnetic moments are parallel to each other. within each domain, a special form of interaction called “exchange coupling ” exists among the adjacent atoms rendering all the dipole moments of all atoms within the domain in the same direction to provide a strong resultant magnetic moment associated with each domain. In the absence of magnetic field they cancel out eachother therefore the ferromagnetic material will remain unmagnetised.

According to this law, magnetic susceptibility(X) is inversely proportional to the absolute temperature(T) of the material.               X ∝ 1/T

Step-I  First of all determine the intercepts of plane on the three co-ordinate axes. Step-II  Secondly, take the reciprocal of these intercepts. Step-III Lastly, reduce the reciprocals into whole numbers. This can be done by multiplying each reciprocal by a number obtained after taking L.C.M. of denominators. ★(h,k,L) is called Miller indices

Space lattice may be defined as an array of points in space such that the environment about each point is the same.

When the electrical resistance of a substance drops suddenly to zero, when it is cooled below a certain temperature, the phenomenon is known as superconductivity.

A laser has a unique combination of coherence,monochromaticity, intensity directionality, which distinguishes it from other light sources. The multiplication of photons through stimulated emission results a coherent, powerful, monochromatic and collimated beam of light known as laser light.