According to the photoelectric effect, the plot of kinetic energy of the emitted photo-electrons from a metal versus the frequency of the incident radiation gives a straight line whose slope

• Correct answer
  A

  is the same for all metals and independent of the intensity of radiation
• B

  depends only on the intensity of radiation
• C

  depends both on the intensity of the radiation and the metal used
• D

  depends on the nature of metals used

Solution

For photoelectric effect, $\phi=\phi_0+(\mathrm{KE})_{\max }$ where, $\phi=$ energy of incident photon $=h v$ $\begin{aligned} & \begin{aligned} & \phi_0= \text { work function of material of metal on } \\ & \text { which photon is falling } \\ &(\mathrm{KE})_{\max }= \text { Maximum kinetic energy of emitted } \\ & \text { photoelectrons. }\end{aligned} \\ & \text { So, on putting the values } \\ & \qquad \begin{aligned} h v=\phi_0+(\mathrm{KE})_{\max } \\ \text { where, } v=\text { frequency of falling photon } \\ \text { and } h=\text { Planck's constant. }\end{aligned}\end{aligned}$
On comparing Eqs. (i) and (ii), we get $m=h=$ constant So, the slope of $(\mathrm{KE})_{\max }$ versus $v$ graph is same for all metals and independent of the intensity of radiation.

Hence, the correct answer is option: 'A'.