The work function of a photosensitive material is $4.0 \ eV$. The longest wavelength of light that can cause photon emission from the substance is approximately $...... \ nm$.

Given below are two statements:
Statement $I$: Stopping potential in photoelectric effect does not depend on the power of the light source.
Statement $II$: For a given metal,the maximum kinetic energy of the photoelectron depends on the wavelength of the incident light.
In the light of the above statements,choose the most appropriate answer from the options given below.

The frequency and the intensity of a beam of light falling on the surface of a photoelectric material are both increased by a factor of two. This will:

$A$ silver ball is suspended by a string in a vacuum chamber and ultraviolet light of wavelength $200 \ nm$ is incident on it. The maximum potential acquired by the ball,if the work function of silver is $4.7 \ eV$,will be .............. $V$.

Photons of energy $6\, eV$ are incident on a metal surface whose work function is $4\, eV$. The minimum kinetic energy of the emitted photo-electrons will be :-

The work function of a certain metal is $2.3 \,eV$. If light of wave number $2 \times 10^6 \,m^{-1}$ falls on it,the kinetic energies of the fastest and slowest ejected electrons will be respectively: