This is an effect observed by Sir J.J Thompson while performing some of his famous experiments. He observed that electrons are ejected by a metal surface when light of a certain frequency strikes the surface of a metal. This phenomenon observed is known as photoelectric ...

The distribution of energy in the spectrum of radiations of a hot body cannot be explained by applying the classical concepts of physics. Max Planck gave an explanation to this observation by his Quantum Theory of Radiation. His theory says: - a)      The Radiant energy is ...

What is a black body? A body which absorbs all the radiations falling at its surface is called a black body. A black body is also a perfect emitter .i.e. emits maximum energy out of all the bodies at same temperature. Whenever a body gets hot, it ...

Atomic Number The total number of unit positive charges present in the nucleus of an atom is known as its Atomic Number which is equal to the number of protons in the nucleus of an atom. Atomic Number for any two different atoms is never same ...

Chadwick performed the same experiment of Rutherford but with beryllium/boron sheet few years after Rutherford’s. He found that new particles carrying no charge and mass almost equal to proton were emitted. This neutral particle is known as neutron. Rutherford suggested an atomic model based upon his ...

Ernest Rutherford performed an experiment in 1911 to know more about the structure of atom. He made a narrow beam of α particles (obtained from polonium) to strike an extremely thin sheet of metal such as gold and silver. A fluorescent sheet was placed behind ...

When careful experiments were carried out using perforated cathode in the discharge tube, a new type of rays known as anode rays were revealed. These rays after emitted by anode pass through the pores made in the cathode surface. These rays carry a positive charge ...

The mass of an electron moving at a velocity much smaller than the velocity of light is known as rest mass. It is calculated by the relation:- M=e/ (e/m) =9.1091X10-31 where e is the charge on an electron e/m is the ratio calculated by Millikan. When the electron ...

Millikan used his famous oil drop technique to determine the charge on an electron. In this experiment, an air containing chamber is injected with an oil spray consisting of microscopic droplets produced by an atomizer. The air is exposed to X-rays and ionized. This ionization ...

A Few years back, we didn’t know the structure of atom; in fact John Dalton considered it to be as hardand dense and as the smallest and indivisible part of matter. But that fact didn’t remain true for long and a new concept in the ...