Question

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

• A. n = 2 to n = 1
• B. n = 4 to n = 3
• C. n = 3 to n = 1
• D. n = 4 to n = 2

Answer 1

Answer: (B)

n = 4 to n = 3

Answer 2

From diagram

$E_{1} = - 13.6 - ( - 3.4) = - 10.2eV$

$E_{2} = - 13.6 - ( - 1.51) = - 12.09eV$

$E_{3} = - 1.51 - ( - 0.85) = - 0.66eV$

$E_{4} = - 3.4 - ( - 1.51) = - 1.89eV$

$E_{3}$ is least i.e. frequency is lowest.