Which properties characterize electromagnetic radiation?

If $p$ is the momentum of the fastest electron ejected from a metal surface after the irradiation of light having wavelength $\lambda$,then for $1.5 \ p$ momentum of the photoelectron,the wavelength of the light should be: (Assume kinetic energy of ejected photoelectron to be very high in comparison to work function)

What is the speed of all types of electromagnetic radiation in a vacuum? What is it called?

The region in the electromagnetic spectrum where the Balmer series lines appear is

The work functions $(W_0)$ of $K, Na, Li, Mg$ and $Cu$ are $2.25, 2.30, 2.42, 3.70$ and $4.80 \ eV$ respectively. How many of these metals do not undergo photoelectric effect when a radiation of wavelength $450 \ nm$ is allowed to fall on them? $(1 \ eV = 1.602 \times 10^{-19} \ J)$

Electromagnetic radiations of frequency $\nu$ consist of a stream of particles called photons. Which of the following statements is / are true about photons: