The work functions (in eV ) of $\mathrm{Mg}, \mathrm{Cu}, \mathrm{Ag}, \mathrm{Na}$ respectively are $3.7,4.8,4.3,2.3$. From how many metals, the electrons will be ejected if their surfaces are irradiated with an electromagnetic radiation of wavelength 300 nm ?

$\left(h=6.6 \times 10^{-34} \mathrm{Js}, 1 \mathrm{eV}=1.6 \times 10^{-19} \mathrm{~J}\right)$

The uncertainty in the velocities of two particles $A$ and $B$ are 0.03 and $0.01 \mathrm{~ms}^{-1}$ respectively. The mass of $B$ is four times to the mass of $A$. The ratio of uncertainties in their positions is

The total maximum number of electrons possible in $3 d$. $6 d, 5 s$ and $4 f$ orbitals with $m_l$ (magnetic quantum number) value -2 is

The radius of fourth orbit in $\mathrm{He}^{+}$ion is ' $R_1{ }^{\prime} \mathrm{pm}$ and radius of third orbit in $\mathrm{Li}^{2+}$ ion is ' $R_2{ }^{\prime} \mathrm{pm}$. The value of ( $R_1-R_2$ ) in pm is