Manipal Entrance Test 2013 Physics Paper

If the maximum kinetic energy of photoelectron emitted from the surface of a metal is EK and W is the work function of the metal, the from Einstein's photoelectric equation we have
EK=hv−W
where, hv is the energy of the photon absorbed by the electron in the metal,
Also v=

c

λ

=

velocity

wavelength

=EK=

hc

λ

−

hc

λ0

=hc(

1

λ

−

1

λ0

)
Given, λ=3×10−7m
λ0=4×10−7m
EK=6.6×10−34×3×108 ×(

1

3×10−7

−

1

4×10−7

)
=

19.8×10−19

12×1.6×10−19

‌eV
=1.03≈1‌eV