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RADIOACTIVITY

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Radioactivity: The uranium salt emitted the rays spontaneously.The phenomenon of spontaneous emission of radiations by heavy elements is called Radioactivity . Properties of nuclear radiation: 1. Properties of Alpha(α) rays: - Alpha(α) particles is a helium nucleus consisting of two protons and two neutrons. - The velocity of α- particles ranges from 1.4 x 10^7 m/s to 2.05 x 10^7 m/s. -They are deflected by electric and magnetic fields. - Alpha (α) particles produce fluorescence in substance like zinc sulphide and barium platinocyanide. - They are massive particles and hence easily stopped by an aluminium sheet of only 0.02mm thick or even by ordinary sheet of paper. - They have great ionising power. Each α-particles produces thousands of ions pairs in a gas before being absorbed. - They get scattered while passing through this metal foils. - They affect a photographic plate. - They can produce artificial radioactivity in certain elements and can produce nuclea...
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Classification of solids

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                            Solids:-    Sol ids : The solids are the forms of matter in which atoms ands molecules are strongly bound and maintain definite volume and sharp unless changes by applying external forces. Solid state physics: - The solid state physics is the study of the physical properties of the atomic/molecular matter in the solids state. These physical properties include crystal structure, bonding,thermal, electric and magnetic properties. Classification of solids:         Solids are classified into two categories; (1) crystalline solids (2) Amorphous solids. (1) crystalline solid :-        The crystalline solids are defined as an ordered periodic arrangements of atoms, molecules or ions . Properties of crystalline solids:- • The internal arrangements of atoms,ions or molecules of crystalline solids is in a definite order. • The crystalline solids have ...
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Photoelectric effect

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Photoelectric effect: when light is incident on a metal surface then electrons are emitted from it. This phenomena is called photoelectric effect.The emitted electrons are called photoelectrons. Laws of photoelectric emissions : 1. The emission of photo-electrons takes place only when the frequency of incident radiation is above certain critical value of that metal.This critical value is called threshold frequency . 2 . The emission of photo-electrons starts as soon as the light falls on metal surface i.e.the photoelectric emission is instantaneous. 3 . The maximum kinetic energy with which the photo-electrons are emitted from a metal surface is independent of the intensity of the light and only depends upon the frequency. 4 . For a given frequency, the number of photo-electrons emitted is directly proportional to the intensity of incident light . 5 .The energy distribution of the photo-electron is independent of the intensity of the incident ...
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