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:

Plot the stopping potential against inverse of wavelength (1/λ) on a graph paper and find

(a) the Planck constant,

(b) the work function of the emitter and

(c) the threshold wavelength.

Question

Philoid · Accepted Answer

(a) from the given table ,

When λ = then V =1.45

∴ from Einstein’s photoelectric equation,

⇒ …..(1)

Again when λ= then V = 1

Then again the equation becomes …… (2)

∴ subtracting eq (1) & (2) we get,

⇒

∴ Planck’s constant,

(b) Substituting the values of h, c (speed of light),

We get the value of Ф (work function) as

∴ Work function, Ф =2.15eV.

(c) We know that work function,

Where λ is the threshold wavelength

h is the Planck’s constant

c is the speed of light

⇒