In an experiment on photoelectric effect, the stopping potential is measured for monochromatic light beams corresponding to different wavelength. The data collected are as follows:
wavelength (nm): 350 400 450 500 550
stopping potential (V): 1.45 1.00 0.66 0.38 0.16
Plot the stopping potential against inverse of wavelength on a graph paper and find (a) the Planck constant, (b) the work function of the emitter and (c) the threshold wavelength .

Explanation

(a) When `lambda = 350, V_s = 1.45 `
and when ` lamdba = 400, V_s = 1`
` :. hc / 350 = w + 1.45 `
and hc / 400 = w + 1 `
Subtracting (2) from (1) and solving to get the value of h , we get
` h = 4.2 xx 10^(-15) ev - sec `
(b) Now, Work function
` w = 12240 / 350 - 1.45 = 2.15 ev. `
(c ) ` w = nc / lambda `
` rArr lambda_threshol = hc / w `
` 1240 / 1.15 = 576.8 nm` .