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Electrons and Photons- Short Question-Answers-4
Electrons and Photons
7. Which metals are suitable for photoelectric effect? Why?Ans: The metals (generally alkali metals) which have low work function are suitable for photoelectric ef
fect. As work function of a metal is the minimum amount of energy required to eject an electron from the surface of the metal (without imparting any kinetic energy), so electrons can be ejected from such metals even by less energetic radiation (i.e. visible light).8. Why does electric discharge take place at low pressure and high potential difference?
Ans: At low pressure and high potential difference, mean free path for the charged particles increased and they acquire sufficient kinetic energy to produce ionization. More ions and electrons are produced in the gas due to collisions. The electrons move towards the anode and the positive ions move towards the cathode. Hence, electric discharge takes place through the gas.
