Question

In a photoelectric experiment, electrons are ejected from metals $X$ and $Y$ by light of frequency $v$. The potential difference $V$ are required to stop the electrons is measured for various frequencies. If $Y$ has a greater work function than $X$, which graph illustrates the expected results?

• A.
• B.
• C.
• D.

Answer 1

Answer: (A)

$e{V}_s=hv-W$
$V_s=\left(\frac{h}{e}\right)v-\left(\frac{W}{e}\right)$
$V_s$ vs $v$ graph is a straight line with constant slope $=\frac{h}{e}$
$\Rightarrow X$ and $Y$ will be parallel.
When $V_s=0,v_0=\left(\frac{W}{h}\right)$
As $W_Y>W_X\Rightarrow v_{0Y}>v_{0x}$
It means the $v$ intercept of $Y$ graph will be larger than the $v$-intercept of $X$ graph.