Homework-13-solns

# Homework-13-solns - Homework 13 Chapter 30 SOLUTIONS...

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QUESTION 1 The filament of light bulb operates at a temperature of about 2665 K. (a) What is the frequency of the most intense radiation from this light bulb? (b) What is the wavelength of this radiation? SOLUTIONS (a) f peak = (5.88 x 10 10 s -1 K -1 ) T = (5.88 x 10 10 s -1 K -1 ) (2665 K) = 1.57 x 10 14 Hz (b) = c / f = (3.0 x 10 8 m/s) / (1.57 x 10 14 Hz) = 1.91 x 10 -6 m QUESTION 2 How many photons are emitted per second by a laser that emits 1 mW of power at a wavelength of 623 nm.  SOLUTION Energy of a single photon:  E  =  h c  /   = (6.63 x 10 -34  J.s) (3.0 x 10 8  m/s) / (623 x 10 -9  m) = 3.193 x 10 -19  J Laser power from  N  photons P = E tot t = N E t N t = P E = 0.001 W 3.193 × 10 19 J N  /  t  = 3.13 x 10 15  photons / sec ond QUESTION 3 The maximum wavelength an electromagnetic wave can have and still eject an electron from a copper surface is 264 nm, What is the work function of a copper surface? (Express your result in the unit of electron-volt). SOLUTION K max  = E  -  :  So electrons will just be ejected when  K max  =  0 W  =  E  =  h c  /   = (6.63 x 10 -34  J.s) (3.0 x 10 8  m/s) / (264 x 10 -9

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Homework-13-solns - Homework 13 Chapter 30 SOLUTIONS...

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