JEE Main · 2009 · 12 Apr 2009 · Offline · Modern Physics

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The surface of a metal is illuminated with the light of 400 nm. The kinetic energy of the ejected photoelectrons was found to be 1.68 eV. The work function of the metal is (hc

= 1240 eV nm

)

(A)3.09 eV
(B)1.41 eV✓ Correct
(C)151 eV
(D)1.68 eV

Answer: (B)

Solution

By Einstein's photoelectric equation the incoming photon energy splits into the work function and the kinetic energy of the ejected electron,

h ν = W_{0} + K E

. The photon energy is

h ν = \frac{h c}{λ} = \frac{1240}{400} = 3.1

eV, and with the measured kinetic energy of 1.68 eV the work function is

W_{0} = 3.1 - 1.68

, which is about 1.41 eV.

JEE Main · 2009 · 12 Apr 2009 · Offline · Single correct option

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