JEE MAIN - Chemistry (2024 - 30th January Evening Shift - No. 23)
Number of spectral lines obtained in $$\mathrm{He}^{+}$$ spectra, when an electron makes transition from fifth excited state to first excited state will be
Answer
10
Explanation
$$\begin{aligned} & 5^{\text {th }} \text { excited state } \Rightarrow n_1=6 \\ & 1^{\text {st }} \text { excited state } \Rightarrow n_2=2 \\ & \Delta n=n_1-n_2=6-2=4 \end{aligned}$$
Maximum number of spectral lines
$$=\frac{\Delta \mathrm{n}(\Delta \mathrm{n}+1)}{2}=\frac{4(4+1)}{2}=10$$
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