Q 40 The maximum kinetic energy of ph... [FREE SOLUTION]

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Chapter 38: Q 40 (page 1115)

The maximum kinetic energy of photoelectrons is 2.8 eV. When the wavelength of the light is increased by 50%, the maximum energy decreases to 1.1 eV. What are (a) the work function of the cathode and (b) the initial wavelength of the light?

Short Answer

Expert verified

a) Work function of the cathode is $2.3 e V$ .

b) Initial wavelength is equal to $243.3 n m$

Step by step solution

Step 1. Given information is :Maximum Kinetic Energy of Photoelectrons = 2.8 eVWavelength is increased by 50%, the maximum energy is decreased to 1.1 eV.

We need to find out :

a) Work function of the cathode

b) Initial wavelength of Light

Step 2. Part a) Using expression of Photo effect

$h f = E_{k m a x} + E_{0} \frac{h c}{位} = E_{k m a x . 1} + E_{0} 1 . \frac{h c}{1.5 位} = E_{k m a x . 2} + E_{0} 2 . D i v i d e 1 b y 2 : \frac{\frac{h c}{位}}{\frac{h c}{1.5 位}} = \frac{E_{k m a x . 1} + E_{0}}{E_{k m a x . 2} + E_{0}} 1.5 (E_{k m a x . 2} + E_{0}) = (E_{k m a x . 1} + E_{0}) 1.5 E_{k m a x . 2} + 1.5 E_{0} = E_{k m a x . 1} + E_{0} 0.5 E_{0} = E_{k m a x . 1} - 1.5 E_{k m a x . 2} E_{0} = \frac{E_{k m a x . 1} - 1.5 E_{k m a x . 2}}{0.5} E_{0} = \frac{(2.8 脳 1.6 脳 10^{- 19} V) - (1.5 脳 1.1 脳 1.6 脳 10^{- 19} V)}{0.5} E_{0} = 2.3 e V$

Step 3. Part b) Using same expression of Wavelength

$位 = \frac{h c}{E_{m a x . 1} + E_{0}} 位 = \frac{(6.63 脳 10^{- 34}) (3 脳 10^{8} m / s)}{(2.8 脳 1.6 脳 10^{- 19} V) + (2.3 脳 1.6 脳 10^{- 19} V)} 位 = 243.3 n m$

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91影视

The maximum kinetic energy of photoelectrons is 2.8 eV. When the wavelength of the light is increased by 50%, the maximum energy decreases to 1.1 eV. What are (a) the work function of the cathode and (b) the initial wavelength of the light?

Short Answer

Step by step solution

Step 1. Given information is :Maximum Kinetic Energy of Photoelectrons = 2.8 eVWavelength is increased by 50%, the maximum energy is decreased to 1.1 eV.

Step 2. Part a) Using expression of Photo effect

Step 3. Part b) Using same expression of Wavelength

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