Question

In the experiment on photoelectric effect, the graph between $E_{K(\max )}$ and $v$ is found to be a straight line as shown in figure. The threshold frequency and Planck's constant according to this graph are

• A. $3.33 \times 10^{18} s ^{-1}, 6 \times 10^{-34} J - s$
• B. $6 \times 10^{18} s ^{-1}, 6 \times 10^{-34} J - s$
• C. $2.66 \times 10^{18} s ^{-1}, 4 \times 10^{-34} J - s$
• D. $4 \times 10^{18} s ^{-1}, 3 \times 10^{-34} J - s$

Answer 1

Answer: (A)

$K_{\max }=h v-W$
$\omega$ is the intercept on $y$-axis and $h$ is the slope.
$\therefore h=\frac{2.4 \times 10^{-15}}{4 \times 10^{18}}=6 \times 10^{-34} Js$
$W=2 \times 10^{-15} J$
$\Rightarrow h v _{0}=2 \times 10^{-15}$
or $v _{0}=3.33 \times 10^{18} s$