JEE Main 2026 · 4 Apr · Shift 1 · Chemistry Q52 · Dronacharya Exams

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What is the ratio of wave number of first line (lowest energy line) of Balmer series of H atomic spectrum to first line of its Brackett series?

A

5:1

B

5:0.81

C

5:1.75

D

5:27

Answer and worked solution

Official answer: B

Wave numbers ( $\propto\frac1{n_1^2}-\frac1{n_2^2}$ ):

Balmer first line ( $3\to2$ ): $\frac14-\frac19=\frac5{36}$ .
Brackett first line ( $5\to4$ ): $\frac1{16}-\frac1{25}=\frac9{400}$ .

Ratio. $\frac5{36}:\frac9{400}=6.17:1=5:0.81$ .

(B)

Topics:Photoelectric effect and spectra Bohr model

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