Write Einstein’s photoelectric equation and mention which important features in photoelectric effect can be explained with the help of this equation.

Question

Write Einstein’s photoelectric equation and mention which important features in photoelectric effect can be explained with the help of this equation.
The maximum kinetic energy of the photoelectrons gets doubled when the wavelength of light incident on the surface changes from l1 to l2. Derive the expressions for the threshold wavelength l0 and work function for the metal surface.

Philoid · Accepted Answer

Einstein’s photoelectric equation is expressed as:

Or,

Where, =maximum kinetic energy of the photoelectron.

=maximum velocity of photoelectron.

m= mass of emitted photoelectron.

= frequency of light radiation.

= work function.

= Planck’s constant.

If is the threshold frequency, then the work function can be written as,

According to the photoelectric equation,

--------- (i)

Let the maximum kinetic energy for wavelength of the incident be,

-------- (ii)

(Given)

From equation (i) and (ii), we get;

Work function is the energy required to eject photoelectron from the metal.