When a radiation of 300 nm is shined on five metals, namely $\mathrm{Li}, \mathrm{Mg}, \mathrm{Ag}, \mathrm{Cu}$ and K , the number of metals that show photoelectric effect are

If the uncertainty in velocity is $\frac{1}{2 m} \sqrt{\frac{h}{\pi}}$, then the ratio of uncertainty in position and momentum is

The total number of spectral lines observed when electron returns from the 6th shell to the 2nd shell in hydrogen atom is

The orbital angular momentum of an electron in $d$-orbital is equal to