On what factors does the magnitude of the velocity of an electron in an orbit depend?

When electromagnetic radiation of wavelength $310 \ nm$ falls on the surface of a metal having work function $3.55 \ eV$, the velocity of photoelectrons emitted is $x \times 10^5 \ ms^{-1}$. The value of $x$ is (Nearest integer). Given: $m_{e} = 9 \times 10^{-31} \ kg$, $h = 6.63 \times 10^{-34} \ J \cdot s$, $c = 3 \times 10^8 \ m/s$, $1 \ eV = 1.6 \times 10^{-19} \ J$.

If the threshold wavelength for a metal is $\lambda_0$ and the wavelength of incident light is $\lambda$,what will be the maximum velocity of the emitted electrons?

The electrostatic force of attraction between the electron and the nucleus in a hydrogen atom is given by:

The masses of photons corresponding to the first lines of Lyman and Balmer series of the spectrum of hydrogen atom are in the ratio of

The ratio of the radii of the $3^{rd}$ and $5^{th}$ orbits of $He^+$ is ..... . (Atomic number of $He = 2$,$r = 0.529 \times \frac{n^2}{Z} \ \mathring{A}$)