- #1

- 971

- 40

## Homework Statement

## Homework Equations

ΔE = hf

## The Attempt at a Solution

f = ΔE/h = ##k\left [ \frac{1}{(n-1)^2} - \frac{1}{n^2} \right ]##

= ## \frac{k(2n-1)}{n^2(n-1)^2}##

= ## \frac{k}{n^4}(2n-1)(1-\frac{1}{n})^{-2}##

= ## \frac{2kn}{n^4}(1-\frac{1}{2n})(1+\frac{2}{n} +## higher powers ## )##

≈ ## \frac{2k}{n^3}(1-\frac{3}{2n}) ## . If I neglect the second term in the bracket , then I get option 3) , but I doubt whether I can do that because I need to retain atleast first order terms .

how should I proceed ?

Any help is appreciated .

Thanks

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