The electric field associated with a light wave is E=E0sin⁡1⋅57×107(x−ct) where x is in metre and t is in second. If this light is used to produce photo-electric emission from the surface of a metal of work-function 1'9 eV, then the stopping potential will be

Given thatE=E0sin⁡1⋅57×107(x−ct)  We know that, E=E0sin⁡2πλ(x−ct)  Comparing, we get λ=2π1⋅57×107m ∴  Energy of photon =hcλ =6⋅64×10−343×1081⋅57×1072π×1⋅6×10−19eV =3⋅1eV So, maximum K.E. of photo-electron =3⋅1−1⋅9=1⋅2eV This is equal to the stopping potential.