The electric field associated with a monochromatic beam becomes zero 1.2 × 1015 times per second. Find the maximum kinetic energy of the photoelectrons when this light falls on a metal surface whose work function is 2.0 eV.
NOTE: In one complete oscillation electric field become
zero twice.
Therefore, if electric field becomes zero times
per second, then number of oscillations per second will
be =
∴ Frequency of the monochromatic light will be Hz
From Einstein’s photoelectric equation, hf=Kmax +Ф
Where h is Planck’s constant,
f is the frequency of light,
Kmax is the maximum kinetic energy,
Ф is the work function
∴ putting the values in the equation we have,
⇒
⇒
⇒
∴ Maximum kinetic energy, Kmax = J.