Question

According to Einstein's photoelectric equation, the plot of the kinetic energy of the emitted photoelectrons from a metal $V_S$ the frequency of the incident radiation gives a straight line whose slope:

• A. depends on the intensity of the radiation
• B. depends of the nature of the metal used
• C. depends both on the intensity of the radiation and the metal used
• D. is the same for all metals and independent of the intensity of the radiation

Answer 1

Answer: (D)

From Einstein's photoelectric equation
$E_k=hv-W$
where $h$ is Planck's constant, $v$ is frequency and $W$ is work function.

Higher the frequency of the incident light, higher will be the maximum kinetic energy of the emitted electrons. If the straight line graph between $E_K$ and $v$ is the extended backwards, it intersects the frequency axis at a point $v_0$ and intersects the energy axis at $-B$. This means that for the photoelectrons to be emitted from a given metal plate, the frequency of the light incident on the plate should be higher than $v_0$. If frequency is less than $v_0$, no photoelectrons will be emitted whatever be the intensity of duration of light. The slope of this plot is $h$ which is constant for all metals.