Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (3rd Edition)

Published by Pearson
ISBN 10: 0321740904
ISBN 13: 978-0-32174-090-8

Chapter 37 - The Foundations of Modern Physics - Exercises and Problems - Page 1121: 4

Answer

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Work Step by Step

$$\color{blue}{\bf [a]}$$ For the Balmer series, we need to use the Balmer formula for the hydrogen atom, $$\lambda=\dfrac{91.18\;\rm nm}{\dfrac{1}{m^2}-\dfrac{1}{n^2}}$$ where $m=1,2,3,...$, and $n=m+1,m+2,m+3,...$ For the first wavelength 102.6 nm, $$ \dfrac{1}{m^2}-\dfrac{1}{n^2}=\dfrac{91.18\;\rm nm}{\lambda_1}$$ $$ \dfrac{n^2-m^2}{m^2n^2}=\dfrac{91.18 }{102.6 }=0.8887$$ This works for $m=\color{red}{\bf 1}$, and $n= \color{red}{\bf 3}$ For the second wavelength 1876 nm, $$ \dfrac{1}{m^2}-\dfrac{1}{n^2}=\dfrac{91.18\;\rm nm}{\lambda_2}$$ $$ \dfrac{n^2-m^2}{m^2n^2}=\dfrac{91.18 }{1876 }=0.0486$$ This works for $m=\color{red}{\bf 3}$, and $n =\color{red}{\bf 4}$ $$\color{blue}{\bf [b]}$$ We know that the visible light is in the range of $$400\;{\rm nm}\lt \lambda_{\rm visible}\lt 700\;{\rm nm}$$ where 400 nm and less is ultraviolet and 700 nm and more is infrared. This means that the 102.6 nm is in the ultraviolet region while the 1876 nm is in the infrared region.
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