What is the threshold frequency of a metal with a work function of $1.65 \ eV$?

When light of wavelength $\lambda$ is incident on a photosensitive surface,the stopping potential is $V$. When light of wavelength $3 \lambda$ is incident on the same surface,the stopping potential is $\frac{V}{6}$. Then the threshold wavelength for the surface is:

When ultraviolet rays are incident on a metal plate, the photoelectric effect does not occur. It occurs by the incidence of:

The photoelectric threshold frequency of a metal is $v$. When light of frequency $4v$ is incident on the metal,the maximum kinetic energy of the emitted photoelectrons is

The slope of the graph between the frequency of incident light and the stopping potential for a given surface is:

Light of frequency $8 \times 10^{15} \ Hz$ is incident on a substance of photoelectric work function $6.125 \ eV$. The maximum kinetic energy of the emitted photoelectrons is ........... $eV$.