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Light | Reflection of Light | Laws of reflection | Classs 10 physics Here we study class 10 physics,optics,light,reflection of light,laws of reflection,plane mirror,reflection by plane mirror,theory of light. Light 1. Light is a form of energy which enables us to see an object. 2.It is an electromagnetic wave. 3.Light waves are transverse in nature. 4.Light waves are electromagnetic radiation so they do not need a material medium to  travel. 5.It travels in vacuum as well as in material transparent medium. 6. The speed of light is 300000km/s in vacuum. 7.The speed of light in material medium is less than in vacuum. 8. Light travels in a  straight line. 9.Light is the fastest messenger in the universe. Theory of Light There are four theories of light. These are 1 . Newton's Corpus cular Theory of Light  : It explains corpuscles/particles nature of light.It proves rectillinear propagation of light, Reflection of light,Refraction of light. It does not prove interference of ...

  Hertz, Hallwacks and Lenard's observation on Photoelectric effect Hertz observation The phenomenon of photoelectric emission was discovered by Heinrich Hertz in 1887, when he was working with his electromagnetic wave experiment. When suitable radiations fall on a metal surface,some electrons near the surface observe enough energy from the incident radiation. Due to it, they are able to overcome the attraction of the positive ions in the material of the surface and escape to the surrounding space. Hallwacks and Lenard’s observation Hallwack and Lenard made a detailed study of the Photoelectric effect during 1886 to 1902. They observed,” when ultraviolet radiation falls on an emitter plate that is positive plate electrons are emitted from it which are attracted towards the other metal plate called collector plate kept at positive potential.The flow of electrons through the evacuated glass tube results in the current flow in the external circuit.  Thus light falling on the surf...

  Electron emission Introduction The phenomenon of emission of electrons from the surface of a metal is called electron emission. Electron emissions are  of following types : Thermionic emission Photoelectric emission Field emission or Cold cathode emission Secondary emission Thermionic emission It is the phenomenon of emission of electrons from the metal surface when heated  suitably.  The energy required for emission of electrons from the metal surface is being supplied by thermal energy.  The emitted electrons are called thermal electrons or thermions.  The number of thermions emitted depends on the temperature of the metal surface. Photoelectric emission The phenomenon of emission of electrons from the surface of metal when light radiation of suitable frequency falls on it  is called Photoelectric effect.  The energy to the free electrons for their emission is being supplied by light Photons.  The emitted electrons are called photoelectro...

                                                                                                                                                    Dual Nature of Matter and Radiation Introduction The discovery of phenomena like interference, diffraction and polarization established that wave of nature. Maxwell’s equations of electromagnetism and Hertz experiment on production and detection of electromagnetic waves in 1886 strongly supported the concept of wave nature of light . The discovery of cathode rays by William Crookes in 1879, of X-rays by Roentgen in 1895 and of electrons by J.J. Thomson in 1897 were very importan...