Linear spectrum (line spectrum) is a characteristic of which of the following?

Which color in the visible spectrum has the minimum energy? State its energy,wavelength,and frequency.

Calculate the frequency of visible light whose wavelength is $456 \, nm$.

Which of the following statements is correct about the photoelectric effect?
$1$. The number of electrons ejected from a metal surface is inversely proportional to the intensity of light.
$2$. Below the threshold frequency,the photoelectric effect can be observed.
$3$. At a frequency higher than the threshold frequency,the ejected electrons have a certain kinetic energy.
$4$. At a frequency higher than the threshold frequency,the electron is still on the metal surface.

What is the wavenumber of a radiation having a wavelength of $0.25 \mu m$?

The wavelength of a spectral line of caesium is $460 \ nm$. What is the frequency of the spectral line?