The ratio of momenta of an electron and an $\alpha - $particle which are accelerated from rest by a potential difference of $100 V$ is
$1$
$\sqrt {\frac{{2{m_e}}}{{{m_\alpha }}}} $
$\sqrt {\frac{{{m_e}}}{{{m_\alpha }}}} $
$\sqrt {\frac{{{m_e}}}{{2{m_\alpha }}}} $
An electron initially at rest, is accelerated through a potential difference of $ 200$ volt, so that it acquires a velocity $8.4 \times {10^6}m/s.$ The value of $e/m$ of electron will be
Three particles having their charges in the ratio of $1 : 3 : 5$ produce the same spot on the screen in Thomson’s experiment. Their masses are in the ratio of
A beam of cathode rays is subjected to crossed electric $(E)$ and magnetic fields $(B).$ The fields are adjusted such that the beam is not deflected. The specific charge of the cathode rays is given by (where $V$ potential diffrence between kethod and anode)
The charge on electron was discovered by
Positive rays consists of