The photoelectric threshold wavelength of a certain metal is $3000 \mathring{A}$. If the radiation of $2000 \mathring{A}$ is incident on the metal,then:

The wave picture of light has failed to explain which of the following phenomena?

The threshold frequency for a metal is $10^{15} \ Hz$. Choose the correct statement when light of wavelength $4000 \ \mathring A$ is incident on it.

Do all the electrons that absorb a photon come out as photoelectrons?

Light of intensity $10^{-5} \; W m^{-2}$ falls on a sodium photo-cell of surface area $2 \; cm^2$. Assuming that the top $5$ layers of sodium absorb the incident energy,estimate the time required for photoelectric emission in the wave-picture of radiation. The work function for the metal is given to be about $2 \; eV$. What is the implication of your answer?

The maximum value of the stopping potential in the following diagram is .......... $V$.