Q.
Order of e/m ratio of proton, a-particle and electron is:
3029
212
Dual Nature of Radiation and Matter
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Solution:
Key Idea: Lighest particle will have highest e/m ratio. The mass of electron =9.1×10−31kg Mass of proton =1.67×10−27kg Mass of a-particle =6.6×10−27kg Since, me ratio is required, e will be same in case of electron and proton but is 2e for α− particle. Hence, that ratio will he highest whose mass (m) is lowest irrespective of charge on α− particle as it does not give greater value to this ratio. As is observed from masses, mass of electron is lowest, therefore e/m ratio of electron is highest. Similarly, α− particle is heaviest, it will have lowest, me ration