College Physics (7th Edition)

Published by Pearson
ISBN 10: 0-32160-183-1
ISBN 13: 978-0-32160-183-4

Chapter 27 - Quantum Physics - Learning Path Questions and Exercises - Exercises - Page 935: 12

Answer

Quantum of violet light has more energy than quantum of red light. $\frac{E_{violet,quanta}}{E_{red,quanta}}=1.75=\frac{7}{4}$

Work Step by Step

Energy of a Quanta of light is given by $E=hf$, since $f=\frac{c}{\lambda}$ Energy of a Quanta of light is $E=\frac{hc}{\lambda}$ wavelength of red light $\lambda_{red}= 700nm=700\times10^{-9}m=7\times10^{-7}m$ $h=6.63\times10^{-34} J.s$, $c=3\times10^{8}m/s$ putting these values we will get $E_{red,quanta}=\frac{6.63\times10^{-34} J.s\times3\times10^{8}m/s}{7\times10^{-7}m}$ $E_{red,quanta}=2.8414\times10^{-19}J$ similarly for violet light wavelength of violet light $\lambda_{red}= 400nm=400\times10^{-9}m=4\times10^{-7}m$ $h=6.63\times10^{-34} J.s$, $c=3\times10^{8}m/s$ putting these values we will get $E_{violet,quanta}=\frac{6.63\times10^{-34} J.s\times3\times10^{8}m/s}{4\times10^{-7}m}$ $E_{violet,quanta}=4.9725\times10^{-19}J$ ratio of the photon energy associated with voilet light to that related to red light $\frac{E_{violet,quanta}}{E_{red,quanta}}=\frac{4.9725\times10^{-19}J}{2.8414\times10^{-19}J}= 1.75=\frac{175}{100}=\frac{7}{4}$
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