MHT CET · Physics · Atomic Physics

For wavelength of visible radiation of hydrogen spectrum Balmer gave an equation as \(\lambda=\frac{\left(\mathrm{km}^2\right)}{\left(\mathrm{m}^2-4\right)}\), where \(m\) is the integer value. The value of \(k\) in terms of Rydberg's constant \(R\) is

A \(\frac{R}{4}\)
B \(\frac{4}{R}\)
C \(R\)
D \(4 R\)

Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{4}{R}\)

Step-by-step Solution

Detailed explanation

Wavelength of visible radiation in Balmer series is given by,
\(\begin{aligned} & \frac{1}{\lambda}=R\left(\frac{1}{4}-\frac{1}{m^2}\right) \text { for } m \geq 2 \\ & \Rightarrow \lambda=\frac{4}{R} \cdot \frac{m^2}{m^2-4}=\frac{k m^2}{m^2-4}\end{aligned}\)
\(\therefore k=\frac{4}{R}\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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