^Photocell Also called electric eye works on the photoelectric effect. Its electrical properties are affected by the amount of light. It can be used as light meters to measure the intensity of light in scientific work. In the reproduction of sound in motion pictures and in the television camera for scanning and telecasting, as burglar […]
^Photoelectric current For a given metal & frequency of incident radiations the no. of photo electrons ejected per second is called photoelectric current it is directly proportional to the intensity of incident light but independent of energy of incident light.
^Kinetic energy of the photoelectrons The kinetic energy of the photoelectrons varies from 0 to Kmax. Maximum KE of photoelectrons is independent of intensity of incident light but depends upon energy or frequency of incident light. It is given by Einstein’s photoelectric equation Kmax = h(f inci. – fth) = eVs Stopping potential versus incident […]
^Photoelectric effect 1. An instantaneous process (10-8 s) of emission of free electrons from the surface of a metal (also called cathode) when light photons of energy greater than threshold frequency are incident on it. 2. Einstein experimentally confirmed that the Photoelectric effect is a one-photon-one electron process & verifies the quantum nature of light […]
^Heisenberg’s uncertainty principle It is impossible to specify preciously and simultaneously the values of both members of canonically conjugate quantities (CCQ) i.e. those quantities which on multiplication give units of action (i.e. Js) e.g. 1. Linear momentum and Linear displacement 2. Energy and Time 3. Angular momentum and Angular displacement. Let c1 and c2 be […]
^Einstein’s mass-energy equivalence The relation is called relativistic energy or Einstein’s mass-energy equivalence as it reveals that mass & energy are interconvertible. Here the quantity m0 c2 is the energy associated with the rest mass of the body, K is the kinetic energy of the body & the sum of KE & rest mass energy […]
^Relativistic mass & energy Mass of a particle moving at speed v (also called relativistic mass) is related to its rest mass m0 & speed of light c as Note here m0 and c are constants.
^Electron microscope The wave properties of electrons have been utilised in the design of electron microscope. Resolving power of an electron microscope is expressed as . Resolving power of electron microscope can be up to 105 times that of optical microscope.
^de – Broglie hypothesis All material microscopic particle have dual nature, i.e. they can behave like particle as well as like a wave. Wavelength associated with a particle of momentum p is given de Broglie waves are also known as Matter waves, pilot waves, stationary waves or probability waves. Theses are neither mechanical (as can […]
^Millikan oil-drop experiment In 1913, Millikan measured the charge on an electron precisely using oil-drop experiment. He found that the charge on an oil-droplet was always an integral multiple of an elementary charge, 1.602 × 10-19 C. Millikan’s experiment established that electric charge is quantised. From the values of charge (e) and specific charge (e/m), […]
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