^Frequency of revolution
^Frequency of revolution
For n = 1, Z = 1; f = 6.57 x 1015 revolutions/s
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^Inertia
^Inertia
Natural tendency to resist change in the state of motion or rest or direction is called inertia. Changes of state means from rest to motion or from motion to rest or from moving in one direction to other. Inertia of a body is proportional to mass of that body. Due to inertia of rest a body at rest has a tendency to remain at rest. Some external force is required to change its state from rest to motion. Force required is more if the inertia of the body is high (i.e. heavy mass). A moving body has inertia of
motion & inertia of direction. Thus its tendency is to oppose a change in state from motion to rest or change in one direction to other direction.
^Velocity of electron in nth orbit
^Velocity of electron in nth orbit
^Radius of nth orbit
^Radius of nth orbit
^Angular momentum quantization
^Angular momentum quantization
An electron can revolve around the nucleus only in those orbits where the circumference of the orbit is integral multiple of the wavelength. Such orbits are called stationary.
Here 
is the minimum value of angular momentum in the first orbit of any H-like atom.
Frank-Hertz experiment (1914) experiment experimentally demonstrated the existence of discrete stationary orbits.
^Bohr’s model
^Bohr’s model
Bohr’s theory It is applicable for single electron system i.e. hydrogen & hydrogen like atoms e.g. He+, Li2+, Be3+
^Rutherford experiment
^Rutherford experiment
In 1911 Rutherford, Geiger & Marsden studied the scattering of alpha particles on passing a narrow beam of alpha particles through a thin gold foil. Conclusions of their experimental in 1913 which led to the discovery of the nucleus.
Rutherford’s model discovered nucleus successfully explained the large angle scattering of alpha particles & justified classification of the elements in periodic table but failed to explain about the stability of atom & also failed to explain the line spectrum of H – atom.
^Davisson & Germer experiment
^Davisson & Germer experiment
This experiment (1927) established the wave nature of slow moving electrons. In this method a fine beam of accelerated electrons is allowed to strike normally on the nickel crystal and then the intensity of scattered electrons in a given direction is found by using a rotate able detector at various scattering angles. Comparing the wavelength of scattered electrons using Bragg’s law & De – broglie the wave nature of electrons can be confirmed.
^Pair annihilation
^Pair annihilation
It is the reverse of pair production effect. Experiments reveal that when a positron passes through matter & sees an electron and the two come together under the influence of their internal electric attraction, may form an atom like configuration called positronium, where they rotate around each other about the centre of mass & ultimately come close together and annihilate (vanish) each other in a time of the order of 10-10 s & the lost mass becomes the electromagnetic energy in the form of two gamma ray photons, each moving away from the other with energy 0.511 MeV in opposite direction such that both energy & linear momentum is conserved.
^Pair production
^Pair production
Actually 1.02 MeV is the rest mass energy of a pair of Electron & positron. If the energy of photon striking the nucleus is greater than 1.02 MeV, then this excess energy is shared equally by the Electron & positron as the KE. Pair production effect can’t take place in vacuum. As it is impossible for pair production effect to conserve both energy & momentum if it take place in vacuum.
