In an experiment on photoelectric effect, the slope of the cut-off voltage versus frequency of incident light is found to be 4.12 × 10–15 V s.
Calculate the value of Planck’s constant.
Photoelectric equation
eV0 = hv - ϕ0 ………… eq.01
Where e = Charge on an electron = 1.6 × 10-19 C
V0 = Stopping Potential
h = plank’s constant
v = frequency of photon
ϕ0 = Work function of the metal
Rewriting equation no. 1
V0 = hv/e - ϕ0/e ………………………………equ.02
h/e is slop of the line represented by above equation02.
Therefore h/e = slop of the line = 4.12 × 10-15 Vs
h = 1.6 × 10-19 × 4.12 × 10-15 = 6.594 × 10-34 Js
Value of plank’s constant ‘h’ from above experiment is equal to 6.594 × 10-34 Js.