Question

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.

Answer 1

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.

solution : given, slope of cut-off voltage versus frequency of incident light = 4.12 × 10^-15 V/s

we know, slope of graph = Plank's constant/charge on electron

or, slope = h/e

so, h = slope × e

= 4.12 × 10^-15 V/s × 1.6 × 10^-19 C

= 6.592 × 10^-34 Js

hence, value of planks constant is 6.592 × 10^-34 J.s