All electrons ejected from a surface by incident light of wavelength 200 nm can be stopped before traveling 1 m in the direction of a uniform electric field of4NC-1. The work function of the surface is
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The work function of the surface is 2.2 eV
Explanation :
The electron ejected with speed V can be stopped by the electric field
Hence KE of the electron = work done by the force field
=> mv²/2 = e x E x d
E = 4 N/c and d = 1 m
=> mv²/2 = 4 eV
The wavelength of the incident light = 200 nm
=> Energy of the incident photon, hv₀ = 1240/200 = 6.2 eV
From the photo electric effect equation we know that,
mv²/2 = hv₀ - Ф₀
=> Ф₀ = hv₀ - mv²/2
= 6.2 - 4
=> Ф₀ = 2.2 eV
Hence the work function of the surface is 2.2 eV
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