Question

What is the maximum number of emission lines when the excited electron of a H atom in n = 6 drops to the ground state?

Answer 1

Number of lines produced when electron from nth shell drops to ground state = n(n-1)/2

Now according to question lines produced when electron drops from 6th shell to ground state

= 6(6-1) / 2 = 15

These are produced due to following transition

6 to 5      5 to 4    4 to 3     3to 2     2 to 1 (5 lines)

6 to 4     5 to 3    4 to 2     3 to 1             (4 lines)  

6 to 3     5 to 2    4 to 1                          (3 lines)

6 to 2     5 to 1                                      (2 lines)

6 to 1                                                    (1 lines)