Which of the following series correctly represents the energy of the radiation?

Find the wavelength of electromagnetic radiation having frequency $1368 \ kHz$. (in $m$)

The momentum (in $kg \cdot m/s$) of a photon having $6 \, MeV$ energy is:

The work functions of $Ag, Mg, K$ and $Na$ respectively in $eV$ are $4.3, 3.7, 2.25, 2.30$. When an electromagnetic radiation of wavelength of $300 \ nm$ is allowed to fall on these metal surfaces,the number of metals from which the electrons are ejected is $(eV = 1.6022 \times 10^{-19} \ J)$

How is an electron observed? Explain.

The wavelength of $X$-ray is $1.5 \times 10^{-10} \ m$. Find the frequency.