IIT-JEE 2007 · Paper 1 · Physics Q9

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PhysicsSingle correct+3 / -1Question 9 of 66

The largest wavelength in the ultraviolet region of the hydrogen spectrum is 122 nm. The smallest wavelength in the infrared region of the hydrogen spectrum (to the nearest integer) is

802 nm

823 nm

1882 nm

1648 nm

Answer and worked solution

Official answer: B

Largest UV wavelength is Lyman $2\to1$ : $\dfrac1{122}=R\left(1-\frac14\right)=\frac34R$ .

Smallest IR wavelength is the Paschen series limit ( $\infty\to3$ ): $\dfrac1\lambda=\dfrac R9$ .

Ratio. $\lambda=\dfrac9R=9\times\dfrac34\times122=823.5$ nm, i.e. 823 nm.

(B)

Topics:Bohr model and hydrogen spectrum

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IIT-JEE 2007 · Paper 1, Physics question 9