Number of bright lines in the emissions spectrum will be

Question

In a sample of hydrogen like atoms all of which are in ground state , a photon beam containing photons of various energies is passed. In absorption spectrum , five dark lines are observed. The number of bright lines in the emissions spectrum will be

A) 5

B)10

C) 15

D) none

Answer 1

Sigma of n-1 n= 6

since 5 dark lines

so Sigma of r-1

where r goes to 6

=>15