PULLA EDU APP JEE MAIN ADVANCED

Particle Nature of Electromagnetic Radiation:  Planck’s Quantum Theory The important postulates of quantum theory proposed by Max Planck are: 1. Atoms and molecules could emit or absorb energy not in a continuous manner, but discontinuously  in small packets of energy called quanta or photons.  2. The energy (E ) of each quantum of radiation is proportional to its frequency (ν). It is expressed by the equation, E = hν Where ‘h’ is known as Planck’s constant and its value is 6.626×10–34 J s. Photoelectric effect It is the phenomenon of ejection of electrons by certain metals (like potassium, rubidium, caesium  etc.) when light of suitable frequency incident on them. The electrons ejected are called photoelectrons.  This phenomenon was first observed by H Hertz. The important characteristics of photoelectric effect are: 1. The electrons are ejected from the metal surface as soon as the beam of light strikes the surface. i.e.,  there is no time lag between the...

Rutherford’s Nuclear Model of Atom Rutherford proposed an atom model based on his α–particle scattering experiment. He bombarded a very  thin gold foil with α–particles. The Experiment: A stream of high energy α–particles from a radioactive source was directed at a thin gold  foil. The thin gold foil was surrounded by a circular fluorescent zinc sulphide screen. Whenever α–particles  struck the screen, a tiny flash of light was produced at that point. Observations: The important observations made by Rutherford are: 1. Most of the α– particles passed through the gold foil without any deviation. 2. A small fraction of the α–particles was deflected by small angles. 3. A very few α– particles (∼1 in 20,000) bounced back, that is, were deflected by nearly 180°. Observations: The important observations made by Rutherford are: 1. Most of the α– particles passed through the gold foil without any deviation. 2. A small fraction of the α–particles was deflected by sm...