The correct answer will be option (C) i.e 1+2+3......(×-1)
Explanation:
Thus the number of lines emitted from nth energy level
= 1 + 2 + 3 +………… n – 1 = ∑(n – 1)
∑n = n(n+1)/2
Thus, ∑ (n – 1) = ( n-1) (n-1+1)/2 = (n-1) (n)/2
Number of spectral lines that appear in spectrum when an electron jumps from nth energy level = n (n-1)/2