When a photon of suitable frequency is incident on a metal surface, photoelectron is emitted from it. If the frequency is below a threshold frequency ($\nu_0$) for the surface, no photoelectron is emitted. For a photon of frequency $\nu$ ($\nu > \nu_0$), the kinetic energy of the emitted photoelectrons is $h(\nu - \nu_0)$. The photocurrent can be stopped by applying a potential $V_0$ called 'stopping potential' on the anode. Thus maximum kinetic energy of photoelectrons $K_{\text{m}} = eV_0 = h(\nu - \nu_0)$. The experimental graph between $V_0$ and $\nu$ for a metal is shown in figure. This is a straight line of slope m. $4 \times 1 = 4$ (i) The straight line graphs obtained for two metals (A) coincide each other. (B) are parallel to each other. (C) are not parallel to each other and cross at a point on $\nu$-axis. (D) are not parallel to each other and do not cross at a point on $\nu$-axis. (ii) The value of Planck's constant for this metal is (A) $\frac{e}{m}$ (B) $\frac{1}{me}$ (C) $me$ (D) $\frac{m}{e}$ (iii) The intercepts on $\nu$-axis and $V_0$-axis of the graph are respectively : (A) $\nu_0, \frac{h\nu_0}{e}$ (B) $\nu_0, h\nu_0$ (C) $\frac{h\nu_0}{e}, \nu_0$ (D) $h\nu_0, \nu_0$