What is value (magnitude) of electric field required for field emission ?

The mass of a particle is $400$ times than that of an electron and the charge is double. The particle is accelerated by $5 V$. Initially the particle remained in rest, then its final kinetic energy will be ........... $eV$

Who invented $X-$ rays? 

Answer the following questions:

$(a)$ guarks inside protons and neutrons are thought to carry fractional charges $[(+2 / 3) e ; (-1 / 3) e] .$ Why do they not show up in Millikan's oil-drop experiment?

$(b)$ What is so special about the combination $e / m ?$ Why do we not simply talk of $e$ and $m$ separately?

$(c)$ Why should gases be insulators at ordinary pressures and start conducting at very low pressures?

$(d)$ Every metal has a definite work function. Why do all photoelectrons not come out with the same energy if incident radiation is monochromatic? Why is there an energy distribution of photoelectrons?

$(e)$ The energy and momentum of an electron are related to the frequency and wavelength of the assoctated matter wave by the relations:

$E=h v, p=\frac{h}{\lambda}$

But while the value of $\lambda$ is physically significant, the value of $v$ (and therefore, the value of the phase speed $v \lambda$ ) has no physical significance. Why?

If an electron oscillates at a frequency of $ 1 GHz$  it gives

An electron of charge $‘e’$ coulomb passes through a potential difference of $V$ volts. Its energy in ‘joules’ will be