8/20/2019 CBSE PHY 1

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 Electron volt (eV) - is a unit of energy. It is defined asthe energy gained by a particle carrying one electroniccharge when it is accelerated through a potentialdifference of 1 volt. 1 eV = 1.6 X 10-19 J.

 Velocity (v) of a charged particle when acceleratedthrough a potential difference of V volt is given by,

v =  (2eV/m).

 Stopping potential- minimum potential required tostop photoelectric emission from a surface.

 

Mass defect of a nucleus is less than the masses of itsconstituent nucleons. This is called mass defect.

 The mass lost by the nucleons is used up to form thenucleus, i.e. to bind the nucleons together. This iscalled binding energy (B.E.). It obeys Einstein’s mass-energy relation. B.E. = mass defect X c2.

 Alpha particles are helium (He) nuclei having 2 unit

positive charge and mass number 4; beta particles areelectrons coming out of the nucleus; gamma rays areenergy photons having zero charge and zero mass.

 The antiparticle of electron is positron as both havesame mass but opposite charge.

 Thorium series is 4n, neptunium series is 4n+1,uranium series is 4n + 2 while actinium series is 4n+3.

 

1 curie = 3.7 X 1010 disintegrations/sec. 1 rutherford = 106 disintegrations/ sec.

 1 becquerel = 1 disintegration/ sec.

 Carbon -14 is used in radiocarbon dating orarchaeological dating to find the age of buildings,rocks, statues etc.

Dr. P. N. PATHAKSASARAM, BIHAR