question_answer

Which of the transitions in hydrogen atom emits a photon of lowest frequency                 (n = quantum number) [BHU 1999]

A)            n = 2 to n = 1                        

B)            n = 4 to n = 3

C)            n = 3 to n = 1                        

D)            n = 4 to n = 2

Correct Answer: B

Solution :

                   From diagram                    \[{{E}_{1}}=-13.6-(-3.4)=-10.2\,eV\]                    \[{{E}_{2}}=-13.6-(-1.51)=-12.09\,eV\]                    \[{{E}_{3}}=-1.51-(-0.85)=-0.66\,eV\]                    \[{{E}_{4}}=-3.4-(-1.51)=-1.89\,eV\]            \[{{E}_{3}}\] is least i.e. frequency is lowest.