The maximum kinetic energy of a photoelectron is $E$ when the wavelength of incident radiation is $\lambda$. If the wavelength of the incident radiation is reduced to $\frac{\lambda}{3}$,the maximum kinetic energy becomes $4E$. The work function of the metal is:

In a photoelectric effect experiment,$f$ is the frequency of radiations incident on the metal surface and $I$ is the intensity of the incident radiations. Consider the following statements. Which of the following statements are correct?
$(A)$ If $f$ is increased keeping $I$ and work function constant,then the maximum kinetic energy of the photoelectron increases.
$(B)$ If the distance between the cathode and anode is increased,the stopping potential increases.
$(C)$ If $I$ is increased keeping $f$ and work function constant,then the stopping potential remains the same and the saturation current increases.
$(D)$ If the work function is decreased keeping $f$ and $I$ constant,then the stopping potential increases.

Two identical photo-cathodes receive light of frequencies $f_1$ and $f_2$. If the velocities of the photoelectrons (of mass $m$) coming out are respectively $v_1$ and $v_2$,then:

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:

The work function of a metal is $4.2 \ eV$. Its threshold wavelength will be .......... $ \mathring A $.

When green light is incident on the surface of a metal, it emits photo-electrons, but there is no such emission with yellow light. Which one of the following colors can produce the emission of photo-electrons?