Which of the following is not an electromagnetic radiation?

In the photoelectric effect,the saturation photocurrent:

The ratio of the energy of a photon with wavelength $3000 \ \mathring{A}$ to that of a photon with wavelength $6000 \ \mathring{A}$ is:

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength $6800 \, \mathring{A}$. Calculate threshold frequency $(v_{0})$ and work function $(W_{0})$ of the metal.

The wavelength range of the visible spectrum extends from violet $(400 \, nm)$ to red $(750 \, nm).$ Express these wavelengths in frequencies $(Hz).$ $(1 \, nm = 10^{-9} \, m)$

Which color in the visible spectrum has the maximum energy? Provide its energy,wavelength,and frequency.