In an experiment of photoelectric effect, the slope of cutoff voltage versus frequency of incident light is found to be 4.12 × 10–15 Vs. Calculate the value of Planck’* constant.
Einstein’* photoelectric equation is Ek = hv – ϕ0
or eV0 = hv – ϕ0
or V0 = h/e v -ϕ0/e
Clearly, slope of V0 – v curve is h/e.
Give h/e = 4.12 x 10-15 V-* ⇒h = 4.12 x 10-15 joule second
= 4.12 x 10-15 x 1.6 x 10-19 = 6.59 x 10-34 Js
