In an experiment on photoelectric effect , the slope of the cut - off voltage versus frequency of incident light is found to be ` 4.12 xx 10^(-15)` V s . Calculate the value of Planck's constant.

Explanation

Given , slope of graph `tan theta = 4.12 xx 10^(-15) V-s,`
`e = 1.6 xx10^(-19)` c.
For slope of graph , `tan theta = V/v`
We know that hv = eV
` V/v = h/e rArr h/e = 4.12 xx 10^(-15) , h = 4.12 xx 10^(-15) xx 1.6 xx 10^(-19) = 6.592 xx 10^(-34) J -s`