A plot of the kinetic energy $\left(\frac{1}{2}{\mathrm{mv}}^2\right)$of ejected electrons as a function of the frequency (v) of incident radiation of four alkali metals ${\mathrm{M}}_{\text{1}}\text{,\hspace{0.17em}\hspace{0.17em}}{\mathrm{M}}_{\text{2}}\text{,\hspace{0.17em}\hspace{0.17em}}{\mathrm{M}}_{\text{3}}\text{,\hspace{0.17em}\hspace{0.17em}}{\mathrm{M}}_{\text{4}}$ is shown below:
 

The alkali metals ${\mathrm{M}}_1,{\mathrm{M}}_2,{\mathrm{M}}_3$ and M₄ are respectively

Kinetic Energy vs Frequency of Ejected Electrons

A plot of the kinetic energy (½ mv²) of ejected electrons as a function of the frequency (ν) of incident radiation for four alkali metals M₁, M₂, M₃, M₄ is shown.

Interpretation and Assignment

• The farther left the line intercepts the frequency axis, the lower the work function (easier to remove an electron).
• The order of threshold frequency for alkali metals is: Cs < K < Na < Li (Li has highest, Cs lowest).
• This means: M₁ = Cs, M₂ = K, M₃ = Na, M₄ = Li

Final Answer

The alkali metals M₁, M₂, M₃, and M₄ are respectively: Cs, K, Na, Li