electromagnetic radiation having 310 A are subjected to a metal sheet having work function 12.8 eV. what will be the velocity of photoelectron with maximum kinetic energy
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Electromagnetic radiation having λ=310
A
˙
is subjected to a metal sheet having work function = 12.8 eV. What will be the velocity of photo electrons having maximum kinetic energy?
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ANSWER
Energy of photon of wavelength, λ=310×10
−10
is
λ
hc
.
Therefore ,E(photon)=
(31×10
−9
)
(6.62×10
−34
)(3×10
8
)
=6.406×10
−18
J.
Work function, W=12.8eV=12.6×1.6x10
−19
J=2.016×10
−18
J.
Now, maximum kinetic energy of photo electron,
(0.5)mv
(max)
2
=E(photon)−W=6.406×10
−18
−2.016×10
−18
J=4.39×10
−18
J.
Therefore,v
(max)
2
=
(9.1×10
−31
)
(4.39×10
−18
)(2)
=9.648×10
12
m
2
s
−2
.
Therefore, v
(max)
=3.106×10
6
ms
−1
Hence,option C is correct answer
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