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

Two light waves of wavelengths $600 \,nm$ and $200 \,nm$ are incident on a metal surface. The maximum velocity of photoelectrons produced due to one wavelength is $\frac{1}{3}$ of the maximum velocity of the photoelectrons produced due to the other wavelength. The work function of the metal is:

Radiation of wavelength $\lambda$ is incident on a photocell. The fastest emitted electron has speed $v$. If the wavelength is changed to $\frac{3\lambda}{4}$,the speed of the fastest emitted electron will be:

The work functions for metals $A, B$ and $C$ are $1.92 eV, 2.0 eV$ and $5 eV$ respectively. According to Einstein's photoelectric equation,which of these metals will emit photoelectrons for an incident radiation of wavelength $4100 \mathring{A}$?

The work function of sodium is $2.3 eV$. The threshold wavelength of sodium will be ........... $\mathring A $

Light emitted during the de-excitation of an electron from $n=3$ to $n=2$ is incident on a metal, and photoelectrons are just emitted from that metal. In which of the following de-excitations is the photoelectric effect $NOT$ possible?