The photoelectric effect shows:

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

Nitrogen laser produces a radiation at a wavelength of $337.1 \ nm$. If the number of photons emitted is $5.6 \times 10^{24}$,calculate the power of this laser.

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 $(eV = 1.6022 \times 10^{-19} \ J)$

$A$ metal surface is exposed to solar radiation.

What changes are observed in the color of iron as it is heated,and how does the frequency of the emitted radiation change?