Which properties characterize electromagnetic radiation?

Explain the properties of electromagnetic waves.

Assuming that the incident radiation is capable of ejecting photoelectrons from all the given metals,the lowest kinetic energy of the ejected photoelectron is observed with which of the given metals?

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

Calculate the energy of one mole of photons of radiation whose frequency is $5 \times 10^{14} \ Hz$.

The energy of an electromagnetic radiation is $19.875 \times 10^{-13} \ erg$. What is its wave number in $cm^{-1}$? $(h = 6.625 \times 10^{-27} \ erg \ sec, c = 3 \times 10^{10} \ cm \ sec^{-1})$