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JEE Main Physics Class 12 Dual Nature of Matter and Radiation Part 1 Questions
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Question : 69
Total: 100
A photoelectric surface is illuminated successively by monochromatic light of wavelengths
λ
and
λ
2
.
If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the surface is :
[Online April 10,2016]
h
c
2
λ
h
c
λ
h
c
3
λ
3
h
c
λ
Validate
Solution:
From Einstein's photoelectric equation
K
.
E
.
λ
=
h
c
λ
−
ϕ
........(i)
(for monochromatic light of wavelength
λ
)
where
ϕ
is work function
K
.
E
.
λ
2
=
h
c
λ
∕
2
−
ϕ
........(ii)
(for monochromatic light of wavelength
λ
∕
2
)
From question,
K
.
E
.
λ
2
=
3
(
K
.
E
.
λ
)
⇒
h
c
λ
∕
2
−
ϕ
=
3
(
h
c
λ
−
ϕ
)
2
h
c
λ
−
ϕ
=
3
h
c
λ
−
3
ϕ
⇒
2
ϕ
=
h
c
λ
∴
ϕ
=
h
c
2
λ
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