Question

Hydrogen atom in its ground state is excited by radiation of wavelength 975 Å. How many lines will be there in the emission spectrum

• A. 2
• B. 4
• C. 6
• D. 8

Answer 1

Answer: (C)

6

Answer 2

Using $\frac{1}{\lambda} = R\left\lbrack \frac{1}{n_{1}^{2}} - \frac{1}{n_{2}^{2}} \right\rbrack$

⇒ $\frac{1}{975 \times 10^{- 10}} = 1.097 \times 10^{7}\left( \frac{1}{1^{2}} - \frac{1}{n^{2}} \right)$

⇒ n = 4

Now number of spectral lines $N = \frac{n(n - 1)}{2} = \frac{4(4 - 1)}{2} = 6$.