Correct Answer - A
`lamda_(1)=(12375)/(E_(1)(eV))`Å=1000Å
`thereforeE_(1)=12.375`eV
similarly, `E_(2)=(12375)/(lamda_(2)("Å"))eV=(12375)/(2000)=6.1875eV`
Now, `E_(1)-W_(0)=eV_(S) and E_(2)-W_(0)=eV_(S)`
`implies 12.375-W_(0)=7.7eV_(S)` . . (i)
`6.1875-W_(0)=eV_(S)` . .. (ii)
Solving the above equations, we get `V_(S)=1.5V`.