1. Tardigrade
  2. Question
  3. Physics
  4. The wavelength of red light is about 760 nm. The work functions of Cs , Na , Cu and Pt are 2.14 eV , 2.75 eV 4.65 eV and 5.65 eV respectively. Which among the following metals can be used as a photosensitive material for red light

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Q. The wavelength of red light is about $760 \,nm$. The work functions of $Cs , Na , Cu$ and $Pt$ are $2.14 \,eV , 2.75 \,eV$ $4.65 \,eV$ and $5.65 \,eV$ respectively. Which among the following metals can be used as a photosensitive material for red light

Dual Nature of Radiation and Matter

Solution:

$E=\frac{h c}{\lambda}, E_{ red }=\frac{1242 \,eV - nm }{760\, nm }=1.63 \, eV$
As $E_{\text {red }}$ is less than the work function of all the metals given in the question, none of the metals will be photosensitive to it.