The photoelectric effect proves that

The work function of a metal is $1.5 \mathrm{eV}.$ Light of wavelength $2500 \stackrel{\mathrm{o}}{\mathrm{A}}$ is incident on this metal. Maximum velocity of photoelectrons is $\underline{ }$
 

Light of wavelength $4000 \mathrm{\AA }$ is incident on a metal plate whose work function is $2 \mathrm{eV}.$ What is maximum kinetic energy of emitted photoelectron?

In a photoelectric experiment, it is found that stopping potential for a given metal is to be $V_o$ volt in presence of wavelength ${\lambda }_o$. When radiation of wavelength  $2{\lambda }_o$ is used with the same metal then what will be the stopping potential (in Volt )?

A graph is plotted between maximum kinetic energy $\left(E_{\mathit{k}}\right)$ of electrons with frequency of incident photon $\left(\nu \right)$ in photoelectric effect. The slope of the curve will be,