Question

A plot of the kinetic energy $\left(\frac{1}{2}m{v}^2\right)$ of ejected as a function of the frequency (v) of incident radiation for four alkali metals $(M_1,M_2,M_3,M_4)$ is shown.
The alkali metals $M_1,M_2,M_3$ and $M_4$ are respectively:

• A. Li, Na, K, and Rb
• B. Rb, K, Na, and Li
• C. Na, K, Li, and Rb
• D. Rb, Li, Na, and K

Answer 1

The correct option is B Rb, K, Na, and Li

For a given kinetic energy, the frequency of incident radiation increases in the order $M_1<M_2<M_3<M_4$. The work function of metals also increases in the same order.
$M_4$ has maximum work function which indicates that valence electron is most tightly bound to the nucleus. This is true for Li.
$M_1$ has minimum work function which indicates that valence electron is most loosely bound to the nucleus. This is true for Rb.
The alkali metals $M_1,M_2,M_3,M_4$ are $Rb,K,Na,Li$ respectively.