Physics - Modern Physics Question with Solution | TestHub

According to Einstein's photoelectric equation, the maximum kinetic energy ($E$) of emitted photoelectrons is given by:

$E=h\nu -\Phi$

where $h$ is Planck's constant, $\nu$ is the frequency of incident radiation, and $\Phi$ is the work function of the metal.

Comparing this equation with the equation of a straight line, $y=mx+c$, we get:
$y=E$
$x=\nu$
Slope, $m=h$ (which is positive)
$y$-intercept, $c=-\Phi$ (which is negative)

The $x$-intercept (where $E=0$) is $\nu =\frac{\Phi }{h}={\nu }_0$, which is the threshold frequency. For frequencies $\nu <{\nu }_0$, no photoelectric emission takes place, so the kinetic energy is zero. For $\nu >{\nu }_0$, the kinetic energy increases linearly with frequency.

Graph (C) correctly shows a straight line with a positive slope and a positive intercept on the frequency axis ($\nu$-axis), representing the threshold frequency ${\nu }_0$.

Answer: C