Physics (10th Edition)

Published by Wiley
ISBN 10: 1118486897
ISBN 13: 978-1-11848-689-4

Chapter 29 - Particles and Waves - Problems - Page 841: 12

Answer

Infrared $253.546\times10$$^2$$^1$ photons Blue light $198.611\times10$$^1$$^9$ photons

Work Step by Step

Given Mass $(m)$$=$ $0.50kg$ Specific heat capacity glass $($$c_°$$)$$=$$840j/kg C^°$ Infrared light wavelength$($$\lambda_l$$)$$=6\times10$$^-$$^5$$m$ Blue light wavelength$($$\lambda_b$$)$$=4.7\times10^-$$^7$$m$ Rise in temperature$($$\Delta$$T)$$=2$ $^°C$ As we know $Q=mc_°$$\Delta$$T$ Here $Q$ is heat energy which can be written as $nhc/$$\lambda$ where $n$ is the number of photons. $nhc/$$\lambda$$=mc_°$$\Delta$$T$ $n=$$($$mc_°$$\Delta$$T$$/$$hc$ $)$$\times$$\lambda$ For infrared light $n=$ $($$0.5\times840\times2$$)/$$($$6.626\times10$$^-$$^3$$^4$$\times3\times10$$^8$$)$ $\times6\times10$$^-$$^5$ $n=253.546\times10$$^2$$^1$photons And similarly for blue light $n=$$($$0.5\times840\times2\times4.7\times10$$^-$$^7$$)$$\div$$(6.626\times10$$^-$$^3$$^4$$\times3\times10$$^8$$)$ $n=198.611\times10$$^1$$^9$photons
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