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hlo friend ur ans is When a beam of lyt with high frequency is made to fall on metallic surface then electrons are made photo electrons.
When light falls on the surface of the metal it ejects electrons. This is photoelectric effect. For this, each metal should posses minimum frequency (threshold)frequency

It is the phenomenon in which the surface of alkali metal like potassium and calcium emit electron on their own when the beam of light with high frequency is made to fall on them
“The phenomenon of ejection of electrons from the surface of a metal when light of suitable frequency strikes on it, is called photoelectric effect.The emitted electrons are called photoelectrons.”Experimental studies of photoelectric effect under different conditions led to the following important observations—(i) The electrons are ejected from the metal surface as soon as the beam of light strikes the surface. .(ii) For each metal, certain minimum frequency of light is needed to eject the electrons. This is known as threshold frequency and it is different for different metals.(iii) The kinetic energy of the ejected electrons is directly proportional to the frequency of the incident radiation and it is independent of its intensity.(iv) The number of electrons ejected per second from the metal surface depends upon the intensity or brightness of incident radiation but does not depend upon its frequency