Hydrogen ( 1 H 1 ), Deuterium ( 1 H 2 ), singly ionised Helium ( 2 He 4 ) + and doubly ionised lithium ( 3…

Hydrogen (1H1), Deuterium (1H2), singly ionised Helium (2He4)+ and doubly ionised lithium (3Li6)++ all have one electron around the nucleus. Consider an electron transition from n=2 to n=1. If the wave lengths of emitted radiation are λ 1 λ 2 λ 3  and λ 4  respectively then approximately which one of the following is correct ?
  1. 4 λ 1 = 2 λ 2 = 2 λ 3 = λ 4
  2. λ 1 = 2 λ 2 = 2 λ 3 = λ 4
  3. λ 1 = λ 2 = 4 λ 3 = 9 λ 4
  4. λ 1 = 2 λ 2 = 3 λ 3 = 4 λ 4

Solution

For radiation, we know that

1λ=RZ21n12-1n22

∴    λ 1 Z 2

λ 1 1 1

λ 2 1 1

λ 3 1 4

λ 4 1 9

∴    λ 1 = λ 2 = 4 λ 3 = 9 λ 4

Asked in: JEE Main 2014 (06 Apr)

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