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Question
Ejection of a photoelectron from a metal in the photoelectric effect experiment can be stopped by applying 0.5 V when a radiation of 250 nm is used. The work function of the metal is :
Ejection of a photoelectron from a metal in the photoelectric effect experiment can be stopped by applying 0.5 V when a radiation of 250 nm is used. The work function of the metal is :
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Solution
The correct option is C 4.5 eV
From Einstein's Photoelectric Equation,
K.E = E − Wo, Also K.E = eVo
eVo = hcλ − Wo
where, Vo = Stopping potential
h = Planck's Constant = 6.626 × 10−34J.s
c = Speed of light = 3 × 108 m/s
λ = Wavelength of incident light = 250 nm = 2.5×10−7 m
We know that 1 eV = 1.6×10−19J
And need to calculate Wo
Putting values in above equation,
We get,
Wo =hcλ−eVo
⇒Wo=(6.62×10−34)(3×108)2.5×10−7−(1.6×10−19)(0.5)=7.14×10−19 J
=4.5 eV
⇒Wo=4.5 eV
From Einstein's Photoelectric Equation,
K.E = E − Wo, Also K.E = eVo
eVo = hcλ − Wo
where, Vo = Stopping potential
h = Planck's Constant = 6.626 × 10−34J.s
c = Speed of light = 3 × 108 m/s
λ = Wavelength of incident light = 250 nm = 2.5×10−7 m
We know that 1 eV = 1.6×10−19J
And need to calculate Wo
Putting values in above equation,
We get,
Wo =hcλ−eVo
⇒Wo=(6.62×10−34)(3×108)2.5×10−7−(1.6×10−19)(0.5)=7.14×10−19 J
=4.5 eV
⇒Wo=4.5 eV
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