Calculate the stopping potential for the photo- elections emitted by gold cathode if the wavelength of incident radiation is 3x10^-7 m, Given that the work function of gold is 4eV.
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Class 12
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>>The photoelectric work function for a me
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The photoelectric work function for a metal is 4.2eV. If the stopping potential is 3V, find the threshold wavelength and maximum kinetic energy of emitted electrons.
(Velocity of light in air =3×10
8
m/s, Planck's constant =6.63×10
−34
J−s, Charge on electron =1.6×10
−19
C)
Medium
Solution
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Given : e=1.6×10
−19
C, c=3×10
8
m/s
ϕ=4.2eV, h=6.63×10
−34
J.s, V
S
=3V
ϕ=4.2×1.6×10
−19
J
=6.72×10
−19
J
(a) Threshold wavelength =λ
0
=
ϕ
hc
=
6.72×10
−19
6.63×10
−34
×3×10
8
=2.960×10
−7
m
=2960
A
˚
(b) Maximum kinetic energy,
KE
max
=eV
S
=1.6×10
−19
×3
=4.8×10
−19
J