What is an emission spectrum?

Which of the following travels with the speed of light?

When electromagnetic radiation of wavelength $300 \, nm$ falls on the surface of a metal,electrons are emitted with the kinetic energy of $1.68 \times 10^5 \, J \, mol^{-1}$. What is the minimum energy needed to remove an electron from the metal? $(h = 6.626 \times 10^{-34} \, J \, s, c = 3 \times 10^8 \, m \, s^{-1}, N_A = 6.022 \times 10^{23} \, mol^{-1})$

The photoelectric effect can be caused by which of the following?

$A$ metal surface is exposed to solar radiation.

Lines of the $Lyman$ series of the spectrum of hydrogen are in