The graph shows the variation of stopping potential $V_o$ with the frequency $\nu$ of the incident radiation for three photosensitive metals $X_1, X_2$ and $X_3$. Which metal will emit photoelectrons with greater kinetic energy, for the same wavelength of incident radiation?

In the photoelectric effect,the stopping potential $(V_0)$ versus frequency $(\nu)$ curve is plotted. ($h$ is Planck's constant and $\phi_0$ is the work function of the metal)
$(A)$ $V_0$ versus $\nu$ is linear.
$(B)$ The slope of the $V_0$ versus $\nu$ curve $= \frac{\phi_0}{h}$.
$(C)$ Planck's constant $h$ is related to the slope of the $V_0$ versus $\nu$ line.
$(D)$ The value of the electric charge of an electron is not required to determine $h$ using the $V_0$ versus $\nu$ curve.
$(E)$ The work function can be estimated without knowing the value of $h$.
Choose the correct answer from the options given below:

In the graph of maximum kinetic energy of photoelectrons emitted from a metal surface versus the frequency of incident radiation based on Einstein's photoelectric equation,the slope is .......

The figure shows the variation of photocurrent with anode potential for four different radiations. Let $f_a$,$f_b$,$f_c$ and $f_d$ be the frequencies for the curves $a$,$b$,$c$ and $d$ respectively.

When a photon of energy $hv$ is incident on an aluminum plate with a work function $E_0$,the maximum kinetic energy of the emitted photoelectrons is $K$. If the frequency of the incident radiation is doubled,the maximum kinetic energy of the emitted photoelectrons will be .......

Ultraviolet radiations of $6.2 \, eV$ fall on an aluminium surface (work function $4.2 \, eV$). The kinetic energy in joules of the fastest electron emitted is approximately: