Question

In a photoelectric effect experiment, the slope of the graph between the stopping potential and the incident frequency will be $\left(\text{in} SI \text{unit}\right)$

• A. $10^{- 14}$
• B. $5\times 10^{- 14}$
• C. $4\times 10^{- 15}$
• D. $4\times 10^{- 34}$

Answer 1

Answer: (C)

When light waves of differing frequencies are made incident on the same surface, the stopping potential ( $V_{s}$ ) differ as is evidenced from Einstein's photoelectric equation given by
$hv-hv_{0}=eV_{s}$
where $h$ is Planck's constant, $v,v_{0}$ the frequencies and $e$ the charge.


Hence, $ \, \, V_{s}=\frac{h v}{e}-\frac{h v}{e}$ ...(i)
Comparing Eq. (i) with straight line equation
$y=mx+c$
Slope $m=\frac{h}{e}$
$Where \, \, \, h=6.6\times 10^{- 34} \, Js, \, e=1.6\times 10^{- 19} \, C.$
$\therefore \, \, m=\frac{6.6 \times 10^{- 34}}{1.6 \times 10^{- 19}}=4.125\times 10^{- 15}$